None
Fig. 173. (3) Original figure of the type of Archewohippus mourning Merriam, Uniy. Cal. Pal. Coll. 19840, dp*~*, ml. One and one-half natural size. (4) 4. ultimus Cope, Univ. Cal. Pal. Coll. 1689, referred upper molar. One and one-half natural size. (5a, 5b) Paratype of A. mourningt Merriam, Univ. Cal. Pal. Coll. 19764, ps-m2. Natural size. After Merriam, 1913, pp. 422, 428. Horizon and locality — Barstow formation, Barstow syncline, Mohave Desert, California. Type collected by H. S. Mourning, Jan. 1913. Type.— Univ. Cal. Pal. Coll. 19840. A portion of a maxillary with milk dentition and m!. Measurements: m! a.p. .0137, tr. .016. Paratype. A portion of a mandible with dentition representing pe-me, Univ. Cal. Pal. Coll. 19764. Type figure.— Text Fig. 173 of this Memoir. Characters.— (Merriam, 1913) (1) Small, brachyodont horse. (2) Metaloph fully united with ectoloph; (3) pro- toloph elongate and lophoid, overlapping left protocone; (4) hypostyle subtriangular; (5) crochet represented by several plate-like projections from outer end of metaloph; (6) cingulum well developed on posterior side; (7) surface of crown somewhat rugose without trace of cement. 214 OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUID&. INDEX. ALPHABETICAL List OF OLIGOCENE, MIOCENE, AND PLIOCENE SPECIES OF EQUID# WITH PRESENT AND REFERENCE, see under species, below. BIBLIOGRAPHY, see under the various species, and p. 2 DENTAL MORPHOLOGY, pp. 3-7 DENTAL TERMINOLOGY, pp. 3-7 FAUNAL HORIZONS, pp. 8-33 e TABLES, pp. 37, 52, 69, 75, 99, 128, 147, 174, 204 GENERA, Altippus, see Parahippus Anchippus, see Parahippus Anchitherium, see Mesohippus, Miohippus, Kalobatippus, Parahippus, Hypohippus Archeohippus, pp. 204, 211-213 Equus, see Protohippus, Pliohippus, Hipparion Hipparion, pp. 173-202 Hippidium, see Pliohippus Hippodon, see Protohippus Hippotherium, see Merychippus, Protohippus, Hipparion Hypohippus, pp. 204-210 Kalobatippus, pp. 69-74 Merychippus, pp. 98-126 Mesohippus, pp. 36-50 Miohippus, pp. 51-68 Neohipparion, see Hipparion Parahippus, pp. 75-97 Pliohippus, pp. 146-172 Protohippus, pp. 127-145 Stylonus, see Merychippus. GENERIC TABLES, pp. 37, 52, 69, 75, 99, 128, 147, 174, 204 GEOGRAPHIC LOCATION OF EQUID HORIZONS, pp. 8-34, 37, 69, 75, 99, 128, 147, 174, 204 GEOLOGIC HORIZONS, HISTORY AND LOCATION OF, pp. 8-33 £ TABLES, EQUID® SPECIES IN GEOLOGIC SUCCESSION, pp. 37, 52, 69, 75, 99, 128, 147, 174, 204 “ DISTRIBUTION OF PRINCIPLE EQUIDAD SPECIES, KEY TO, p. 34 INDICES, p. 3 LIFE ZONES, SEE ABOVE UNDER FAUNAL HORIZONS MorpHOLOGY OF THE TEETH, under respective species, AND pp. 3-7 be “© uIMBS, “ . e = pDao=h CRANIUM AND SKELETON, under respective species, AND pp. 3-7 SrectEs, alphabetical list of Oligocene, Mio- cene, and Pliocene species of Equide, with Present and Original Generic “ “ “ ORIGINAL GENERIC Reference PRESENT GENERIC REF. OrIGINAL GENERIC REF. acutidens Sinclair 1905, Miohippus (Mesohippus), pp. 52, 64-65. affine Leidy 1869, Hipparion (Hipparion), pp. 174, 178-179. affinis Leidy 1858, Hypohippus (Anchitherium (Hypohippus) affinis), pp. 204, 207-208 agatensis Osborn sp. nov. Kalobatippus pp. 69, 71-73 agrestis Leidy 1873, Parahippus (Anchitherium agreste), pp. 75, 86-87 anceps Marsh 1874, Miohippus (Anchitherium), pp. 52, 58 annectens Marsh 1874, Miohippus (Miohippus), pp. 52, 63-64 anthonyi Merriam 1916, Hipparion (Hipparion), pp. 174, 189 assiniboiensis Lambe 1905, Mesohippus (Mesohippus), pp. 37, 41 atavus, see pawniensis australis Leidy 1873, Parahippus (Anchitherium (?) australe), pp. 75, 85 avus Marsh 1874, Parahippus (Protohippus), pp. 75, 87-89 bairdii Leidy 1850, Mesohippus (Palxotherium, Anchitherium), pp. 37, 45-46 brachylophus Cope 1878, Miohippus (Anchitherium), pp. 52, 60 brachystylus Osborn 1904, Miohippus (Mesohippus), pp. 52, 54 INDEX. 215 Species, alphabetical list of, continued a“ PRESENT GENERIC Reger. ORIGINAL GENERIC ReEr, brevidens Marsh 1874, Parahippus (Anchippus), pp. 75, 89-90 calamarius Cope 1876, Merychippus (Hippotherium calamarium), pp. 99, 123-125 ? calamarius, propinquus p. 28 californicus Merriam 1915, Merychippus (Merychippus), pp. 99, 121-122 calodonte, see mohavense campestris Gidley 1907, Merychippus (Merychippus), pp. 99, 114-115 eastilli Cope 1885, Protohippus (Protohippus), pp. 128, 141-142 celer Marsh 1874, Mesohippus (Anchitherium), pp. 36-38 coalingensis Merriam 1914, Pliohippus (Protohippus), pp. 147, 165-166 cognatus Leidy 1858, Parahippus (Anchitherium (Parahippus)), pp. 75, 94-95 coloradense Osborn sp. nov. Hipparion pp. 174, 183-184 coloradensis Gidley 1907, Parahippus (Parahippus), pp. 75, 93-94 coloradensis precurrens Osborn sp. nov. Parahippus pp. 75, 83 condoni Leidy 1871, Miohippus (Anchitherium), pp. 52, 63 condoni Merriam 1915, Hipparion (Hipparion), pp. 174-176 copei Osborn and Wortman 1895, cumminsil Cope 1893, Pliohippus (Equus), pp. 147, 168-169 cuneatus Cope 1873, Mesohippus (Anchitherium), pp. 37, 47 crassicuspis Osborn 1904, Miohippus (Miohippus), pp. 52, 57-58 crenidens Scott 1893, Parahippus (Desmatippus), pp. 75, 90-92 dolichops Gidley 1906, Hipparion (Neohipparion), pp. 174, 182-183 eohipparion Osborn sp. nov. Merychippus pp. 20, 99, 117-119 eoplacidus Osborn sp. nov. Merychippus pp. 20, 99, 114, 117 equiceps Cope 1878, Miohippus (Anchitherium), pp. 52, 59-60 equinanus Osborn sp. nov. Miohippus pp. 52, 65-66 equinus Scott, Hypohippus (Anchitherium equinum), pp. 203-206. eulophus Osborn 1904, Mesohippus (Mesohippus), pp. 37, 49 eurystyle Cope, 1893, Hipparion (Equus), pp. 174, 186-187 exoletus Cope 1873 Mesohippus (Anchitherium exoletum), pp. 37, 47 fairbanksi Merriam 1915, Pliohippus (Pliohippus), pp. 147, 164 fossulatus Cope 1893, Pliohippus (Protohippus), pp. 147, 156-158 fraternus, Leidy, (see Hipparion princeps) gemmarose Osborn sp. nov. Miohippus pp. 52, 66-68 gidleyi Osborn 1904, Miohippus (Mesohippus), pp. 52, 56-57 gidleyi Merriam 1915, Hipparion (Neohipparion), pp. 174, 187-188 gracilis Marsh 1892, Kalobatippus (Pliohoppus), pp. 69, 71 gracile Kaup 1833, Hipparion (Equus (Hippotherium) gracilis), Pl. 39.5 gratum Leidy 1869, Hipparion (Hipparion), pp. 174, 179-180 gratum tehonense Merriam 1916, Hipparion (Neohipparion), pp. 174, 190 hypostylus Osborn 1904, Mesohippus (Mesohippus), pp. 37, 41 ingenuum Leidy 1885, Hipparion (Hippotherium), pp. 174, 191 insignis Leidy 1857, Merychippus (Merychippus), pp. 99, 122-123 ? insignis obliquus p. 28 intermedius Osborn and Wortman 1895, Miohippus (Mesohippus), pp. 25, 54 intermontanus Merriam 1915, Merychippus (Merychippus), pp. 99, 121 interpolatus Cope 1893, Pliohippus (Hippidium interpolatum), pp. 147, 158, 160 isonesus Cope 1889, primus Osborn sp. nov. tertius Osborn sp. nov. quartus Osborn sp. nov. quintus Osborn sp. nov. labrosus Cope 1874, secundus Osborn sp. nov. Colodon, Miohippus crassi- cuspis Merychippus Merychippus Merychippus (Mesohippus), pp. 52, 57-58 (Hippotherium isonesum Cope, H. seversum Cope), pp. 99, 101-103 pp. 99, 102, 104 pp. 99, 105 pp. 99, 105-106 pp. 99, 107 pp. 99, 107-108 (Protohippus), pp. 99, 109-110 latidens Douglass 1904, Mesohippus (Mesohippus), pp. 37, 39 leidyanus Osborn sp. nov. Pliohippus, pp. 147, 162-163 lenticulare Cope 1893, Hipparion (Protohippus), pp. 174, 184-185 leonensis Sellards 1916, Parahippus (Parahippus), pp. 75, 95-96 leptode Merriam 1915, Hipparion (Neohipparion), pp. 174, 197 longicristis Cope 1878, Miohippus (Anchitherium), pp. 52, 61 lullianus Troxell 1916, Pliohippus (Pliohippus), pp. 147, 159-160 matthewi Barbour 1914, Hypohippus (Hypohippus), pp. 204, 209-210 meteulophus Osborn 1914, Miohippus (Mesohippus), pp. 51-53 minimus Douglass 1908, Parahippus (Anchitherium), pp. 75, 96-97 minor Sellards, Hipparion (Hipparion), pp. 174, 192-193 minutus Cope 1893, Pliohippus (Equus), pp. 147, 169-170 216 OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUID. Specigs, alphabetical list of, continued ORIGINAL GENERIC REP. Pliohippus (Merychippus), pp. 147-148 Merychippus (Meryshippus?), pp. 99, 119-120 Hipparion (Hipparion (?)), pp. 174, 193-194 ( ( PRESENT GENERIC REF. mirabilis Leidy 1858, missouriensis Douglass 1908, mohavense Merriam 1913, mohavense callodonte Merriam 1915, Hipparion Hipparion), pp. 174, 194-195 molle Merriam 1915, Hipparion Neohipparion), pp. 174, 196 montezuma Leidy 1883, Hipparion | (Hippotherium), pp. 174, 1987 mourningi Merriam 1913, Archxohippus (Parahippus (?)), pp. 204, 213 nebrascensis Peterson 1907, Parahippus (Parahippus), pp. 75, 79-80 nebrascensis primus Osborn sp. nov. Parahippus, pp. 75, 80, 82 nevadensis Merriam 1913, Hypohippus (Hypohippus (Drymohippus) nevadensis), pp. 204, 208 niobrarensis Gidley 1906, Protohippus (Neohipparion), pp. 128, 135 nobilis osborn sp. noy. Phohippus, pp. 147, 160-161 obliquidens Osborn 1904, Mesohippus (Mesohippus), pp. 37, 48-49 obliquus, see ? insignis occidentale Leidy 1856, Hipparion (Hipparion), pp. 174, 176-177 osborni Gidley 1907, Hypohippus (Hypohippus), pp. 204, 207 pachyops Cope 1893, Protohippus (Protohippus), pp. 128, 138-139 paniensis Cope 1874, Merychippus (Hippotherium paniense), pp. 99, 109 parvulus Marsh 1868, Protohippus (Equus), pp. 128, 130, 132-133 patruus Osborn sp. nov. Merychippus, pp. 99, 126 pawniensis Gidley 1907, Parahippus (Parahippus), pp. 75, 92-93 pawniensis atavus Osborn sp. nov. Parahippus, pp. 75, 80-81 peninsulatum Cope 1885, Hipparion (Mippotherium), pp. 174, 198-199 perditus Leidy 1858, Protohippus (Equus (Protohippus) perditus), pp. 128-131 perditus secundus Osborn sp. nov. Protohippus pp. 128, 144-145 pernix Marsh 1874, Pliohippus Pliohippus), pp. 147, 151-155 phlegon See Pliohippus minutus Cope, pp. 147, 169-170 placidus Leidy 1869, Protohippus Protohippus), pp. 128, 183-135 planidens Lamhe, 1905, Mesohippus (Mesohippus), pp. 37, 44 platystyle Merriam 1915, Hipparion (Neohipparion, Hippotherium), pp. 174, 188 pheatile Leidy 1887, Hipparion Hippotherium), pp. 174, 192 portentus Douglass, 1908, Mesohippus Mesohippus), pp. 37, 40-41 precocidens Lambe, 1905, Mesohippus Mesohippus), pp. 387, 42-43 preecurrens, see coloradensis KXalobatippus Anchitherium), pp. 69, 70-71 prestans Cope 1879, primus Osborn sp. nov. Miohippus pp. 52, 61-62 primus, see Isonesus primus, see nebrascensis princeps Leidy 1890, Equus (Hippotherium, Hipparion), pp. 174, 201-202 pristinus Osborn sp. nov. Parahippus DD: 79; (0-00 profectus Cope 1889, Protohippus (P. or H. profectus), pp. 128, 142-144 proparvulus Osborn sp. nov. Merychippus pp. 20, 99, 117-118 propinquus Lambe 1905, Mesohippus (Mesohippus), pp. 37, 42-43 propinquus, see calamarius proplacidus Osborn sp. nov. Protohippus pp. 128, 139-141 proteulophus Osborn 1904, Mesohippus (Mesohippus), pp. 37, 41-42 proversus Merriam 1917 Phohippus (Pliohippus), pp. 147, 170-172 quartus Osborn sp. nov. Miohippus pp. 52, 62-63 quartus, see isonesus quintus, “ rectidens Cope 1886, Hipparion (Hippotherium), pp. 174, 199-200 relictus Cope 1889, Merychippus (Hippotherium relictum), pp. 99, 100 republicanus Osborn sp. noy. Merychippus pp. PRESENT GENERIC REP. Hippodon Pliohippus Merychippus Meryehippus Mesohippus Merychippus calamarius Merychippus Phohippus Plohippus Parahippus tertius, see isonesus tehonense, see gratum tehonensis Merriam 1915, texanus Leidy 1868, trigonostylus Osborn sp. nov. tyleri Loomis 1908, ultimus Cope 1886, validus Osborn 1904, var. isonesus var. venustum Leidy 1859, westoni Cope 1889, whitney Gidley 1903, zitelli Schlosser 1903 Protohippus Parahippus Mesohippus, Parahippus Areheohippus Miohippus Merychippus, Mesohippus Hipparion Mesohippus Hipparion Hypohippus (see Protohippus) (Hippodon), pp. 128, 129 OrIGINAL Generic Rer. (H. spectans), pp. 147, 164-165 (Hippotherium), pp. 99, 112-115 (Mesohippus), pp. 37, 48-44 (Merychippus stylodus), pp. 99, 125 (Merychippus), pp. 99, 120-121 (Protohippus), pp. 147, 149-150 (Pliohippus?), pp. 147, 162-163 (Altippus), pp. 75, 85-86 (Protohippus), pp. 128, 138-139 (Anchippus), pp. 75, 84 pp. 37, 47-48 (Parahippus), pp. 75, 77-78 (Anchitherium ultimum), pp. 204, 211-212 (Mesohippus), pp. 52, 55-56 Pl. 10.3 Pl. 2.13 (HMippotherium), pp. 174, 200-201 (Anchitherium), pp. 37-39 (Neohipparion), pp. 174, 181 (Anchitherium), Pl. 35.8 bo = SYSTEMATIC DESCRIPTION AND REVISION, see under respective species, pp. 1, 37, 52, 69, 75, 99, 128, 147, 174, 204, and alphabetical list of species, above TYPE DESCRIPTIONS OF EQuip.® SPECIES, under respective species, pp. 1, 36-213 “ “ , tables of, in chronologic order, pp. 37, 52, 69, 75, 99, 128, 147, 174, 204 te gy i As i Seo 219 Koti SO r eng As At iseSe The teeth in all the Plates are drawn natural size. The skulls are drawn one-half natural size. The limbs and feet are drawn one-half natural size. PLATE 1 SKULLS: MESOHIPPUS, MIOHIPPUS PLATE 27 TYPE, PLIOHIPPUS LULLIANUS : 2 UPPER TEETH: MESOHIPPUS " 28 UPPER TEETH: PLIOHIPPUS : 3 UPPER TEETH: MIOHIPPUS i 29 TYPE, PLIOHIPPUS LEIDYANUS 4 UPPER AND LOWER TEETH: MIOHIPPUS e 30 x a i 5 TEETH, FEET: MIOHIPPUS, HYPOHIPPUS : 31 TEETH: PLIOHIPPUS, HIPPARION e 6 FACE: MIOHIPPUS, ARCH HOHIPPUS, ETC. i 32 FACE: HIPPARION i 7 SKULL: PARAHIPPUS ss 33 TEETH: PLIOHIPPUS, HIPPARION 3 8 UPPERAND LOWER TEETH: PARAHIPPUS _ 34 MILK TEETH: MERYCHIPPUS, PROTOHIP- “ 9 - a “ ae 5 PUS, HIPPARION - 10 FACE: MERYCHIPPUS i 35 SKULL AND TEETH: HYPOHIPPUS s 11 i “ , OF PROGRESSIVE a 36 HIND FEET: PARAHIPPUS Pm TYPE ia 37 FEET: PARAHIPPUS i 12. SKULL: MERYCHIPPUS SPHENODUS = 38 SKELETON: PARAHIPPUS a 13 UPPER TEETH: MERYCHIPPUS 39 CARPUS: MIOCENE HORSES > 14 UPPER AND LOWER TEETH: MERYCHIP- e 40 SKELETON: KALOBATIPPUS PUS ss 41 FORE FEET: MERYCHIPPUS a 15 UPPER TEETH: MERYCHIPPUS e 42 FEET: ‘ 16 . Ss = . 43 FORE FEET: 4 « ws > 4 : 44 s : « - 18 SUPERIOR-INFERIOR MOLAR TOOTH ‘ 45 HUMERUS AND TIBIA: MERYCHIPPUS TYPE: MERYCHIPPUS 46 ULNA AND RADIUS: < ° 19 LOWER TEETH: MERYCHIPPUS . 47 HUMERUS: a Z 20 SKULL AND LOWER TEETH: MERYCHIP- i 48 ULNA AND RADIUS: - PUS is 49 ¢ i " 21 FACE: PROTOHIPPUS 50 FEMUR AND TIBIA:. a 22 TYPE TEETH: PROTOHIPPUS zs 51 TARSUS: ANCHITHERIINE, HYPOHIPPUS 23 FACE: PROTOHIPPUS, PLIOHIPPUS if 52 HIND FEET: MERYCHIPPUS ¥ 24 TEETH: PROTOHIPPUS, PLIOHIPPUS 2 53 ‘ i a a 25 MILK TEETH: PARAHIPPUS-HIPPARION i 54 “ - 3 a 26 FACE: MERYCHIPPUS, PLIOHIPPUS 221 PLATE. I. SKULLS, MESOHIPPUS, MIOHIPPUS. PEA SKULLS OF MESOHIPPUS AND MIOHIPPUS FROM THE LOWER, MIDDLE, AND UPPER OLIGOCENE. All figures natural size. The Mesohippus crania are arranged in ascending systematic and geologic order and exhibit progressive increase in size from the small skulls of the Titanotherium zone to the larger skulls, such as the juvenile M. obliquidens, of the Middle Oreodon zone. Indications of the preorbital fossze are observed in the smallest and most ancient of these horses. Left column Cheyenne River, So. Dak. Lower Oligocene 1. Mesohippus proteulophus Osborn, referred specimen, Am. Mus. 1208 (reversed in drawing). « « Sa tase i “ 2. M. hypostylus, Osborn, type, Am. Mus. 1180 (partly reversed in drawing). ? ? fe. We ? ? 3. M. bairdii Leidy, type. Mus. Cat. No. not known. Type lost. és ‘ ae i. 4. M. bairdii Leidy, neotype, Am. Mus. 1477 (partly reversed in drawing). a - as Middle 4 5. M. obliquidens Osborn, type, Am. Mus. 668 (reconstructed in drawing). Cedar Creek, Col. z A 6. M. eulophus Osborn, type, Am. Mus. 8791 (partly reversed in drawing). Right column. Cheyenne River, So. Dak. Upper 7. Miohippus meteulophus Osborn, type, Am. Mus. 1210, ss i > a & 8. M. brachystulus Osborn, type, Am. Mus. 11860. . ‘ i as 5 = 9. M: intermedius Osborn and Wortman, type, Am. Mus. 1196. : aac - ‘i 10. M. gidleyi Osborn, type, Am. Mus. 1192. . a oom : ce 11. M. validus Osborn, type, Am. Mus. 1218. The smallest of the Miohippus crania exceeds in size the largest crania of Mesohippus from the Upper Oreodon zone. The Miohippus crania exhibit a progressive increase in size. The three skulls from the river channel sandstones of the -Protoceras zone, namely, M. intermedius, M. gidleyi, M. validus, are believed to be of the same geologic age as the lower levels of the Leptauchenia zone. Memoirs Am. Mus. Nat. Hist. Wo. 879/ Type (p.rev.) A.M. “pper_Ureogon Zone No. 668 Type freconsfructioa) A.M. Middle Oreodon Zone Noi /277 weorype (p.rex) eee {4Qwer Oreogon Mesohippus bairdii a oe aoe Type MEL Ra after Leidy 2? Lower Oreodon : Zone Mesohippus _ bairdii No. 1180 Type (p.rev.) A, M1. Upper Titanotnerium Zone Mesohippus hypostylus Ie kh x NO. 1208 Crev) ref. 2 A. 14. Upper Titanorherium Zone Mesohippus proteulophus N.S., Vol. II, Plate 1. We. /218 Type A. /. Proroceras Zone a Miohippus — validus See ee Aine iy i Soa No. {192° Type if NAY if) Miohippus gidleyi Sree Proteceras Zone No. 1496 Type AoAg) YP — Protoceras Zone Miohippus intermedius —e Se We. 11860 Type AL/4. Leptauchenia Zone Miohippus brachystylus No. 42/0 2 A.”. ale Leptauchenta Zone Miohippus mefeulophus * PLATE 2. i UPPER TEETH, MESOHIPPUS. | PAA ee UPPER TEETH OF MESOHIPPUS FROM THE LOWER AND MIDDLE OLIGOCENE. All figures natural size except 11 which is twice natural size, and 13 which is one-half natural  Lower Oligocene “ os 10: sale 12. 13. Left column. Mesohippus montanensis Osborn, type, Am. Mus. 9662 (reversed in drawing). . proteulophus Osborn, type, Am. Mus. 514a (reversed in drawing). . hypostylus Osborn, type, Am. Mus. 1180. T. bairdii Leidy, neotype, Am. Mus. 1477. . trigonostylus Osborn, paratype, Am. Mus. 673. . trigonostylus Osborn, type, Am. Mus. 674. . obliquidens Osborn, type, Am. Mus. 668. . eulophus Osborn, type, Am. Mus. 8791. Right column. . celer Marsh, holotype, Yale Mus. 11302. . westoni Cope, type, Ottawa Mus. 6289. . ? var., referred specimen, Am. Mus. 9326, indet.* M. ? sp. referred specimen, Mus. Comp. Zool. 6547. . bairdii, specimen and record indet. (Composite drawing from different individuals). Dental characters of the Mesohippus stage are observed in the evolution from Mesohippus montanensis of the Lower Titanotherium zone through seven specific stages of ascending mutations to Mesohippus eulophus of the Upper Oreodon zone. Note the gradual evolution of the hypostyle as a bud from the posterior cingulum, attaining a permanent triangular form in MW. trigonostylus of the Metamynodon sandstones, which are channel deposits contemporary with the Lower Oreodon clays. Thus the M. bairdii stage and M. trigonostylus stage are believed to be nearly contemporaneous. *This progressive molar series is recorded from the Upper Oreodon zone of Pawnee Buttes; the correlation is somewhat uncertain. Memoirs. Am. Mus.Nat. Hist. N.5., Vol. II, Plate 2. oo \ No 879/ Troe KS y Yoper Oreodor zone ane ee We. 668 Type SS S== A /? = ‘ A4iddle Oreodon = ee a] SS RIS Meschippus bairdiy No. 674 e Rapes Ito A7eTAM ynodor AM : Ke NG a \ k zone Mesohippus Trigonosfylus ea aie ee =, MoO. O547 ref, Hrorv. us. Comp. Zool. Mesohippus @ spec. No. 673 Paratype Aas 7: de tamynodtor OMe NO. (477 NWeorype A /? LOE IORCOCL OT? EO 72 GC: VO. GS26 ref. ; _ ?uppEer Oreodon Zone Mesohippus ‘var. SS Gos GF | Mesohippus hypostylus WVvo S/4a Type (eK) Tale ACE IN “vpper Jitanorneriam one mS Mesohi ppus westont Mesohippus proteulophus Yale Mus a RON ao ie [= (1g U ar Wate FI > WO. 9662 7Yype crev.) Ansa LZower Titanotherium Zone iat e Meschippus celer Derdicd pas Mesohippus montanensis PLATE 3. UPPER TEETH, MIOHIPPUS. PLATE 3. UPPER TEETH OF MIOHIPPUS FROM SOUTH DAKOTA AND OREGON. Cheyenne River, So. Dak. Lower Rosebud, So. Dak. “ “ce “ “ Middle John Day, Ore. John Day River, Ore. Cheyenne River,  natural size. Left column. Miohippus meteulophus Osborn, type, Am. Mus. 1210 (partly re- versed in drawing). M. brachystylus Osborn, type, Am. Mus. 11860. M. intermedius Osborn and Wortman, type, Am. Mus. 1196. M., gidleyi Osborn, type, Am. Mus. 1192. M. validus Osborn, type, Am. Mus. 1218 (partly reversed in drawing). M. equinanus Osborn, type, Am. Mus. 12912. M. gemmarosa, type, Am. Mus. 13808 (partly reversed in drawing). Right column. M. quartus Osborn, type, Am. Mus. 7267. M. brachylophus Cope, referred specimen, Am. Mus. 7262. M. equiceps Cope, type, Am. Mus. 7261. M. primus Osborn, type, Am. Mus. 7291 (reversed in drawing). M. annectens Marsh, cotype or referred specimen, Yale Mus. 12230. M. condoni Leidy, type, Acad. Nat. Sci. Phila. (drawn from Leidy’s figure). M. crassicuspis Osborn, type, Am. Mus. 683 (reversed in drawing). M. annectens Marsh, type, Yale Mus. 11275. The upper teeth included within the Mzohippus stage extend from the species M. meteulophus of the Leptauchenia zone to those of M/. gemmarose@ of the Promerycocheerus zone of the Lower Rosebud. They are distinguished by variations in size, by varying degrees of development of the hypostyle, which is rudimentary in M. meteulophus, an elongate loop in M. brachystylus, a triangular fold in M. intermedius, M. validus, and M. gemmarose, and by the progressive development of the protoconule and metaconule. w bo Co Memoirs Am. Mus. Nat. Hist. N.5S., Vol. II, Plate 3. NO. 11275 Type tp.rev) oo eae yale /tus. =Y. = \ Zp SZASS>S ~ nt N0./58O8P Tepe Co.rev?) Bg ad bis oN 2» = Miohipe us gem marosée Promeryctocnoerus Zone 4 M0. 1429/2 Type A S/@7. FPromervecthnoerus Zone Miohippus equinanus Miochippus annectens 1 1 : } il Miohippus primus 11 we senrygeired 12 Si ierte,Z¥e8 ORE ae ee bel Ne Serie San al (COG N ane \ yy, 4 \ F eS 1 Miohippus condoni No, 4/92 Type Ae a YP Michippus gidleyi Protoceras Zone Vo. 4/96 Type A. /7, P Preroceras Zone Miohippus equiceps No. //G60 Type A, 9 Miohippus brachystylus Leotaucnernta Zone Michip pus brachylophus Vo. 7267 Type A.M. We. /2/0 Type (p. rev Ae Miohippus meteulophus eS IREE OES ee —~ YF Py, > Tre ~~ *.. PLATE 4. Poe ’ 8. UPPER AND LOWER TEETH, MIOHIPPUS. PLATE 4. UPPER AND LOWER TEETH OF MIOHIPPUS FROM SOUTH DAKOTA AND OREGON. Teeth natural size. Skulls and jaws one-half natural size. Left column. Pine Ridge, So. Dak. Lower Miocene 1. Muiohippus gemmarose, Osborn, paratype, Am. Mus. 12928. A ; ae a ‘ 2. M. gemmarose Osborn, paratype, Am: Mus. 13809. - . ees 3 3. M. gemmarose Osborn, paratype, 12917e. : : sane x i 4. M. gemmarose Osborn, paratype, 12917a. Right column. John Day River, Ore. ss uy 5. M. primus Osborn, type, Am. Mus. 7291 (partly reversed in ‘ drawing). ; i : is , . 6. M. quartus Osborn, paratype, Am. Mus. 7285 (partly reversed in drawing). a 3 : ss ‘S a 7. M. acutidens Sinclair, type, Univ. Cal. Pal. Col. 376. s x i c Upper 8. M. quartus Osborn, type, Am. Mus. 7267 (reconstructed in drawing). Pine Ridge, So. Dak. Lower sy 9. M. gemmarose Osborn, type, Am. Mus. 13808. 230 e Memoirs Am. Mus. Nat. Hist. N.8., Vol. II, Plate 4. 1B 0. /29/7a Paratype A, Miohippus gem marosde Miohippus quartus MO. 376 Type URLLAGAE, Miiohippus acutidens Miohip pus quartus LD VO 7285 Paratype (p.rev.) ~~" A. AT > Miohippus gemmarosde No. 729/ Type (p.rey.) AG , Miohippus primus PLATE 5.— _ : . _ TEETH, FEET, MIOHIPPUS, HY POHTIPPUS. a 40 > PLATE 5. TEETH AND FEET OF MIOHIPPUS, KALOBATIPPUS, ANCHITHERIUM, HYPOHIPPUS. COMPARISON OF THE TEETH AND FEET OF THE OLIGOCENE AND MIOCENE ANCHITHERES. All figures natural size, except 12 and 13 which are one-half natural size. Figs. 1-9. Last lower molar of Miohippus sp. div., Kalobatippus, Anchitherium, and Hypohippus, showing the reduced third lobe, or hypoconid, in the two latter genera. Figs. 10-11. Upper teeth of Kalobatippus Osborn and of Anchithertum, showing the reduction of m* and closing of the postfossette in Anchitherium, greater antero-posterior elongation of the teeth, and more perfected lophodonty. Figs. 12-13. Metatarsals of Kalobatippus Osborn and of Anchitherium, showing the relative slenderness of the former but with unreduced lateral digits. John Day, Ore.’ Middle John Day, Ore. Upper John Day, Ore. Lower Harrison, Agate, Nebr. Georgensemund, Bavaria. gensg Pawnee Creek, Col. Upper John Day, Ore. Sansan, France. Upper John Day, Ore.. Sansan, France. Upper Oligocene “ “ Lower Miocene “ “ Middle Miocene “c “ Upper Oligocene Middle Miocene Upper Oligocene Middle Miocene 10. 11. 12. 13. Miohippus longicristis Cope, Am. Mus. 7268, referred specimen. M. quartus Osborn, Amer. Mus. 7293, referred specimen (reversed in drawing). M. brachylophus Cope, Am. Mus. 7281, referred specimen. M. equiceps Cope, Am. Mus. 7287, referred specimen, unworn molar (reversed in drawing). M. equiceps Cope, type, Am. Mus. 7261, partly worn molars. Kalobatippus prestans Cope, type, Am. Mus. No. 7269. K. agatensis, type, Am. Mus. 14211 (reversed in drawing). Anchitheritum aurelianense, Am. Mus. 10746, referred specimen (reversed in drawing). Hypohippus osborni Gidley, type, Am. Mus. 9407. Kalobatippus prestans Cope, type, Am. Mus. 7269. Anchitherium aurelianense Cuv. (drawn from Kowalevsky’s figure). Kalobutippus prestans Cope, type, Am. Mus. 7269. Anchitherium aurelianense (drawn from Kowalevsky’s figure). Memoirs Am. Mus. Nat. Hist. ING S Volvdiy Plate: CRS ° 4 \ Nee ss 4 No, 9407 Type a A.M, H ypohippus osborni Kalobalippu s prdestans NO. 10746 (rev) ref. ; A. 4. Anchitherium aurelianense After Kowalevstxy WVo.742// Type (rer) A.M. Kalobatippus Anchitherium aqalensis aurelianense 10’ V0.7 269 Tyve A. Ww. Kalobatippus prdestans Gs 5 d c 1 Gui SS INOS) WO.726/ Type ALM, equiceps NO. 7287 (revi ref Ai O75 equiceps M ichip pus M ichippus ae ' MVOC) Let, \ f Ae 7 ‘ \ \ 1 i oe ae \ ! 1 ' ' ! ' Miohippus brachylophus 8 Z S al G A 1 SS WSIS No. 7293 (rev) ref. A. 4. quartus We. 72697y0e! | AT. | Michippus ed Kalobati ppus prdestans N0.7268 ref. A. 7. longicristis 4,005, PLATE 6. FACE, MIOHIPPUS, ARCHHZOHIPPUS, ETC. PLATE 6. PREORBITAL FOSSA IN OLIGOCENE AND MIOCENE EQUIDA FROM OREGON, COLORADO, SOUTH DAKOTA AND NEBRASKA. (Left column) Comparison of front of skull in Miohippus, Archeohippus, Kalobatippus, and Hypohippus. (Right column) Comparison of front of skull in species of Parahippus and Merychippus. The lachrymal fossa is broad and comparatively shallow in the later species. Middle John Day, Ore. Maseall, Ore. Upper John Day, Ore. Pawnee Creek, Col. Lower Rosebud, Pine Ridge, 50. Dak: Upper Harrison, Sioux Co., Nebr. Sheep Creek, Sioux Co., Nebr. Mascall, Ore. The malar fossa is not differentiated. All figures one-half natural size. Upper Oligocene 1, Middle Miocene 2. Uppermost Oligocene, 3. transitional to Lower Miocene Middle Miocene 4. Lower Miocene in. “ “ 6. Middle i the “ “ce 8. Left column. Miohippus equiceps, type, Am. Mus. 7261. Lachrymal fossa broad, shallow; malar fossa not differentiated. Archeohippus ultimus Cope, type, Am. Mus. 8174. Lachry- mal and malar fossz deep, well differentiated. Kalobatippus prestans Cope, type, Am. Mus. 7269. Lachry- mal fossa broad, rather shallow; malar fossa not differen- tiated. Hy pohippus osborni Gidley, type, Am. Mus. 9407. Lachry- mal fossa deep, contracted; no malar fossa. Right column. Parahippus pristinus Osborn, type, Am. Mus. 12918. P. nebrascensis primus Osborn, type, Am. Mus. 13770. P. avus Marsh, referred specimen, Am. Mus. 14182 (reversed in drawing). Merychippus isonesus Cope, type, Am. Mus. 8175. ak a. ie a a Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 6. Merychippus isonesus No. 7269 Type Asian “ee 5 = iO / ws No. /3770 Type A 74. No. 8174 TY Penge Ed No. 726/ Ty, Wee, a Parahip pus pristinus Lae Miochippus equiceps bb. in. i a hy wees - ' a 7 oie ‘ . i ” ' : 7 7 : ee r . - ti ero, 7 . aie on + - + oe / Par va i se i es. 1 i aif : ms : - : J ae te ob? ro ‘ j 7 7 ‘ . . as 4 pes +2 :. , Seg “i z % -¥ i ae 1 i , t ” avy " 7 re . ‘ : ar os. ‘ ‘ = ‘ . 7 ‘. mC. 4 : . , Me .. an : : Aas 7 oy F " : ; ers te ty ae a8 7 ' fe ‘ “s ate iy PINIB, 79 SKULL, PARAHIPPUS. Pall Andi Hiear TYPE SKULL AND LOWER JAWS OF PARAHIPPUS NEBRASCENSIS PRIMUS OSBORN. All figures one-half natural size. Amer. Mus. 13770, type. This skull belongs to a fully adult male and consequently shows very clearly the dis- tinctive characters of the Parahippus skull stage. The crochet is well developed on the superior molar teeth. The hypo- style is simple and does not show the progressive hypostyle fold, the pli hypostyle. This male skull, which was found in the Lower Miocene of the Upper Harrison near Agate, Nebraska, is more pro- gressive than the type skull of P. nebrascensis Peterson, which belongs to a female. In this male skull the facial region is relatively longer. 7 236 Memoirs Am. Mus. Nat. Hist. N.8., Voi. II, Plate 7. p)!' ( Ga |} Ve 2 MeN } \ J WS 7 ———— 1H Oe a ie US UES Ve ae Ky No. 13770 Type A. 4. ( NUS ae , Z = TE ——— : “LY 4 2 Farahip pus nebrascensis primus PLATE. 8. \ UPPER AND LOWER TEETH, PARAHIPPUS. PEAT E28; UPPER AND LOWER TEETH OF PARAHIPPUS FROM THE MIOCENE AND LOWER PLIOCENE. COMPARISON OF MOLAR-PREMOLAR SERIES IN DIFFERENT MIOCENE SPECIES. Upper Rosebud, S. D. Near Agate, Nebraska Upper Rosebud, S. D. Deep River, Mont. Pawnee Creek, Col. Sheep Creek, Nebr. Pawnee Creek,  Middle Miocene il wo 9. All figures natural size. Left column. Parahippus coloradensis precurrens Osborn, paratype, Amer. Mus. 12925. P. nebrascensis primus Osborn, type, Am. Mus. 13770. P. texanus Leidy, referred specimen, Am. Mus. 12924. P. crenidens Scott, type, Princeton Mus. 10430 (drawing from cast, Am. Mus. 10782). P. pawniensis Gidley, type, Am. Mus. 9085 (reversed in drawing). P. avus Marsh, referred specimen, Am. Mus. 14182. “P. coloradensis Gidley, paratype, Am. Mus. 9412. P. cognatus Leidy, referred specimens, Am. Mus. 13919, 13943. Right column. Parahippus avus Marsh, type, Yale Mus. 11281, lower teeth and jaw frag- ment containing po—m, of the right side. P. avus Marsh, type, Yale Mus. 11281 (m! reversed in drawing). P. brevidens Marsh, type, Yale Mus. 11274, two unworn molars, m8 of the left side. P. coloradensis Gidley, type, Amer. Mus. 9040, an unworn m? of the left side, and a worn molar, ?m!', of the right side. o Be eee Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 8. Parahip pus coloradensis 12 Parahippus cognatus No. 94/2 Paratype A. Parahippus coloradensis Parahippus avus Parahip pus pawniensis Parahip pus crenidens / . i / = F a iN 1 i << Ih, ‘ , oll 1 \ My =a i i | A ~l @y Y : DS) i QnA ot aM L(RSD a 2 Y ) S 1 (BLL - We. (0450 Type (Drawn from cast?) ; princeton a OSL NE aS Parahippus avus 10 f \ Parahip pus texanus MO a a No. 1/281 Type. 2 yale ns Parahippus avus Lense Parahip pus coloradensis praecurrens ae. eee Ge os et E PLATE 9. aa r ' 2 ‘ ’ UPPER AND LOWER TEETH, PARAHIPPUS. — r = - 7 - [ rn | Pal Ane 92 UPPER AND LOWER TEETH OF PARAHIPPUS FROM THE LOWER AND MIDDLE MIOCENE. All figures natural size. These are all primitive species not far removed from Miohippus of the Upper Oligocene, especially P. pristinus Osborn of the transition beds. In P. pristinus Osborn observe the extraordinary position of the pli prefossette, similar to that in Miohippus gidleyi Osborn and different from that in P. coloradensis precurrens Osborn, ete. Left column. Agate, Sioux Co., Nebr. Lower Miocene 6. P. tyleri Loomis, referred specimen, Am. Mus. 13769, lower teeth. : Pine Ridge, So. Dak. : i 7. Parahippus pristinus Osborn, type, Am. Mus. 12918. Near Agate, Sioux Co., Nebr. ‘ ‘ 8. P. tyleri Loomis, referred specimen, Am. Mus. 13769, upper teeth. : . a ae . : 9. P.nebrascensis primus Osborn, type, Am. Mus. 13770. Pine Ridge, So. Dak. By : 10. P. tevanus Leidy, referred specimen, Am. Mus. 12924. Right column. Pine Ridge, So. Dak. Z 1. Parahippus coloradensis precurrens Osborn type, Am. Mus. 13018. Deep River, Mont. Middle “ 2. P. crenidens Scott, type, Princeton Mus. 10430 (reversed in drawing). Pawnee Creek, Col. 2 fe 3. P. pawniensis Gidley, type, Am. Mus. 9085 (reversed in drawing). Sioux County, Nebr. i 5g 4. P. avus Marsh, referred specimen, Am. Mus. 14182. Tooth much worn. ?Lower Pliocene 5. P. cognatus Leidy, referred specimen, Am. Mus. 14322. 240 Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 9. In Parahippus cognatus Parahippus avus Parahippus nebrascensis primus “es ANG LOAN wee = Oy YO) 8 : We. {3769 ref jEay5 a Parahippus pawniensis Vo, 0430 Type (rer) Princeton Pa rahippus ty leri Woe. /23/8 Type AGS YP. : (= Aw a Sig Ke ; ey PIs S02 Parahippus crenidens Parahippus co loradensis prdecurrens Last Parahippus tyleri oP LARE Oy FACE, MERYCHIPPUS. = Driftwood Creek, Nebr. Pawnee Creek, North- eastern Colorado Deep River, Mont. Masceall, John Day Basin, Ore. PA Oe PREORBITAL FOSSA IN MERYCHIPPUS. COMPARISON OF SKULLS IN THREE SPECIES. All figures one-half natural size. Merychippus republicanus Osborn, type, Am. Mus. 8347. This is the skull figured by Cope under the name Hippotherium speciosum Leidy. Lachrymal fossa shallow, obscure; no Lower Pliocene ie malar fossa. Middle Miocene 2. M. sphenodus Cope, referred specimen, Am. Mus. 9390. Lachry- mal fossa deep, constricted; no malar fossa. iG is 3. M. isonesus var., referred specimen, Am. Mus. 8105. Lachrymal fossa deep, extensive; malar fossa obscurely separated. ct ‘ 4. M. isonesus Cope, type, Am. Mus. 8175. Lachrymal fossa deep, extensive; malar fossa obscurely separated. 242 Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 10. \ Ze Y 7 x a Hy, y : 1 / a ‘ Lea oe - ay a ‘ ! { \ No. 8347 Type q A. /7. 5 ed ie aa Merychippus tsonesus., PLATE 11. FACE OF MERYCHIPPUS, OF PROGRESSIVE TYPE. - \ : ‘ 243 Pawnee Creek, Northeastern Colorado Snake Creek, Sioux County, Nebr. PEAT BE. wae. PREORBITAL FOSS IN MERYCHIPPUS. COMPARISON OF SKULLS IN FOUR SPECIES. All figures one-half natural size. Middle Miocene ?Lower Pliocene L bo 244 Merychippus sejunctus Cope, type, Am. Mus. 8291. Lachrymal and malar fossee shallow, obscurely separated. M. paniensis Cope, referred specimen, Am. Mus. 9382. Lachrymal fossa deep, extensive; malar fossa not differ- entiated. M. proparvulus Osborn, type, Am. Mus. 9394. No malar fossa. M. calamarius Cope, referred specimen, Am. Mus. 14001-2. Lachrymal and malar fossz distinct, well differentiated. Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 11. es PR i Beas Pig Pry y _- P feat eee / eS ? A ei a ae ! See , Bee Bee / fea VO FOO = 2 Tex, ; ; ' al A. M4. Fhe i as = Ne. 9394 Type Se aso ( / A. S4. J tol t—__ ith aoa >. BO oe ae bermmcn AE  rs i / PERN Ae eee ae ton aa eee ty N ors \ ! pot Shas 0 Soe ; i We. SIE2 FreFf. he oe Se ait week i H A. *4. s PHacatt ee li . g ig t ee ~/ ia ‘ t PC ea Tee eee ieee ees eetranete eee es cee 1 oe j j ie _ *. Meryc ig taaecd Reid LVDS I 2D f. 7Y, e A. 14. Piss Merychippus sejunctus PLATE 12. SKULL, MERYCHIPPUS SPHENODUS. PLAY BL: NEOTYPE SKULL OF MERYCHIPPUS SPHENODUS COPE. One-half natural size. Merychippus sphenodus Cope, neotype, Princeton Mus. 12291 (partly reversed in drawing). This finely preserved skull in the Princeton collection was found by Dr. W. J. Sinclair in Logan County, Colorado, about a mile west of Sand Cafion, in the Middle or Upper Miocene. In the structure of its superior molar teeth it agrees much more closely with the type of M. sphenodus than the specimens which Cope selected as the cotype of that species. The molars are distin- guished by the duplication of the pli caballin as well as of the pli prefossette and pli postfossette. The geologic age is almost certainly typical Pawnee Creek. All referred specimens of M. sphenodus come from this level (W. D. M. 1918). The type of M. sphenodus Cope is recorded as “ Pawnee Creek,” but the exact locality is not known. The author is indebted to Dr. W. J. Sinclair for the opportunity of figuring this skull. 246 Memoirs Am. Mus. Nat. Hist. N.5., Vol. II, Plate 12. \\ 2 \\ \\ eee AED q \ 2 : AI AN \ \ a ana an \ « ‘ \\\ N0./229/ Neotype Princeton /7us. Merychippus sphenodus ere AT sae UPPER TEETH, MERYCHIPPUS. PLAT Has. UPPER TEETH OF MERYCHIPPUS FROM MONTANA, OREGON, AND NEBRASKA. COMPARISON OF VARIOUS SPECIES FROM MIDDLE MIOCENE FORMATIONS OF THE WESTERN UNITED STATES. Mascall, Ore. Middle Miocene Deep River, Mont. . 2 Sheep Creek, Sioux Co., Nebr. “ “ “ Mascall, John Day Middle Miocene Basin, Ore. Mascall (?) “Oregon i Desert” All figures natural size. 1. Merychippus isonesus Cope, type, Am. Mus. 8175. 2. M. isonesus Cope, referred specimen, Am. Mus. 8105. Upper teeth, much By ies thee worn. M. isonesus primus Osborn, type, Am. Mus. 14187. Teeth littie worn. 3, Crown view, 3a, outer view of m’*. . isonesus secundus Osborn, type, Am. Mus. 14179. Teeth less than half worn (partly reversed in drawing). M. isonesus tertius Osborn, type, Am. Mus. 14180. Teeth half worn. 5, Crown view, 5a, outer view of m?. . sonesus tertius Osborn, referred specimen, Am. Mus. 14183. Teeth much worn. (Reversed in drawing). M. isonesus quintus Osborn, type, Am. Mus. 14185. Teeth little worn. _ 7, Crown view, 7a, outer view of m?. 8. Merychippus seversus Cope, type, Amer. Mus. 8180. Upper molar, little worn (reversed in drawing). 9. Merychippus relictus Cope, type, Amer. Mus. 8673. Upper molar, about half worn. 248 “ yY ; 3 = xy y) ag x mI £ 3 ro) Se > y 3 ae D — Xs n 0 Ay ~ w = in IN) ae o- = s = a — 6 § 5 ie) ei . e ool Oo) ie) wi > a : , \ a j | « ! ¥ é aS 1 K oe by ‘ : \ S : i u H ® NS Is \ S K ! 2 \ < i) ue ~ ee 9 S 8 E ee n (6) os 3 S itp) ”) 13) : : : 5 ° y 2) oe ro) ae e 9) y) =] 3 roe a= = ‘3 3 = e) Oo > 7 a a a S \s Memoirs Am. Mus. Nat. Hist. //O€ C0. Fev) he No. 4/4/79 T7 Looe) bd secundus isonesus Merychippus TY pe. Wo. 7/4/60 SY. \ AS K 8 ee NaN v SIN 33 S _ =~ 6 8 \ ry. S %) oe ye oe g* 0) <5) 2) aS iS e fe = 10) + ‘ OF on n =} =| g g 2 = e} e) 2 ee w w =] Are o- fo OS io = « sie Vv ~ ey AS NS Q i) N Aw rs ete Alri, AUG Pas aD PLATE 14. ‘UPPER AND LOWER TEETH, MERYCHIPPUS. * Pag AD ila UPPER AND LOWER TEETH OF MERYCHIPPUS FROM THE SHEEP CREEK BEDS, NEBRASKA. Comparison of three species from Sioux County, Nebraska. The upper teeth of the Sheep Creek specimens of Mery- chippus are compared in crown view on Plate 13, the limbs and feet on Plates 41, 45, 46, 52. All figures natural size. Sheep Creek, Middle Miocene 1. Merychippus isonesus quintus Osborn, type, Am. Mus. 14185. Crown view of Nebr. these teeth is given on Plate 13. . os y 2. Merychippus isonesus primus Osborn, type, Am. Mus. 14187. Upper teeth, outer view. Crown view of these teeth is given on Plate 13. ‘ es 2 3. Merychippus isonesus tertius Osborn, type, Am. Mus. 14180. Outer view of upper and lower dentition. Crown view of upper teeth on Plate 13. ‘ Yi 4. Merychippus isonesus primus Osborn, type, Am. Mus. 14187. Lower teeth. Crown and outer views. . ’ i Memoirs Am. Mus. Nat. Hist. N.5S., Vol. II, Plate 14. / Ne. 4/87 Type A. 14. LAO Mery chippus isone sus primus PLATE 15. UPPER TEETH, MERYCHIPPUS., PLATE 15. UPPER TEETH OF MERYCHIPPUS FROM NORTHEASTERN COLORADO, THREE SPECIES FROM THE MIDDLE MIOCENE OF COLORADO. COMPARISON OF EARLY AND LATE STAGES OF WEAR. All figures natural size. Pawnee Creek, northeastern Colt. Middle Miocene 1. Merychippus sphenodus Cope, cotype, Am. Mus. 8281 (reversed in drawing). This “cotype”’ belongs to a distinct species, more primitive than the type. a us “ i i 2. M. sphenodus Cope, type, Am. Mus. 8281. Teeth little worn (partly reversed in drawing). af te € oe ss 3. M. sphenodus Cope, referred specimen, Am. Mus. 9400. Teeth well worn. 4 at . : y. zs M. campestris Gidley, type Am. Mus. 9096. Teeth little worn, ad f . bs ‘ : 5. M. campestris Gidley, referred specimen, Am. Mus. 9459 (re- versed in drawing). Teeth much worn. u s c s a . 6. M. proparvulus Osborn, type, Am. Mus. 9394. Teeth much worn. ae as é a “ cs 7. M. proparvulus Osborn, paratype, Am. Mus. 9398. Teeth much worn. 252 Memoirs Am. Mus. Nat. Hist. N.8., Vol. II, Plate 15. Merychippus sphenodus V0. G28/ Type Cp.rev) aN He jhe P Merychippus campestris Merychippus campestris Lae Merychippus pro parvulus PLATE 16. UPPER TEETH, MERYCHIPPUS. Pawnee Creek, northeastern Col. PLATE 16, UPPER TEETH OF MERYCHIPPUS FROM NORTHEASTERN COLORADO. COMPARISON Middle Miocene 1. OF UPPER TEETH OF M. SEJUNCTUS AND M. PANIENSIS. All figures natural size. - Merychippus sejunctus Cope, referred specimen, Am. Mus. 8254 (reversed in drawing). Teeth little worn. M. sejunctus Cope, referred specimen, Am. Mus. 9414 (m? re- versed in drawing). Teeth moderately worn. M. sejunctus Cope, type, Am. Mus. 8291, Teeth much worn. M. paniensis Cope, referred specimen, Am. Mus. 9460 (m?-8 reversed in drawing). Teeth little worn. M. paniensis Cope, referred specimen, Am. Mus. 9093. Teeth moderately worn. M. paniensis Cope, referred specimen, Am. Mus. 9039 (reversed in drawing). Teeth much worn. 254 N.5S., Vol. II, Plate 16. Memoirs Am. Mus. Nat. Hist. PLATE 17, UPPER TEETH, MERYCHI PPUS. PLATE 17. UPPER TEETH OF MERYCHIPPUS. COMPARISON OF VARIOUS SPECIES FROM THE MIOCENE AND LOWER PLIOCENE FORMATIONS OF THE WESTERN UNITED STATES. All figures natural size. Masceall, Cottonwood Creek, Ore. Middle Miocene ?Masceall, Oregon Desert, Ore. ?Middle ef Deep River, Mont. Middle Mascall, Cottonwood Creek, Ore.. Niobrara River, Nebr. Lower Pliocene Republican River, Nebr. Driftwood Creek, Nebr. “ 3 Snake Creek, Sioux County, Nebr. ?Lower Pliocene — 8. Merychippus seversus Cope, type, Am. Mus. 8180, (?) of the right side (reversed in drawing). Little worn. M. relictus Cope, type, Am. Mus. 8673, upper molar of the right side. Much worn. M. isonesus Cope, referred specimen, Am. Mus. 8105. Much worn. M. isonesus Cope, type, Am. Mus. 8175. Merychippus insignis Leidy, referred specimen. M. patruus Osborn, type, Am. Mus. &8347a. moderately worn. Upper teeth, M. republicanus Osborn, type, Am. Mus. 8347, upper teeth, moderately worn. (This is ‘the specimen figured by Cope under the name Hippotherium speciosum.) M. calamarius Cope, referred specimen, Am. Mus. 14003. P? and m® are drawn from other (unnumbered) individuals from the same quarry. (M® reversed in drawing.) 256 Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 17. Me rychippus calamarius No. GZ47 Type A. /4- Mierychippus republicanus Merychippus palruus After Lecdy ref. insignis Merychippus vw) 0. G/I75 Type No. 8/80 Type (re L 1 A Merychippus seversus Merychippus isonesus Meryct ippus reliclus Merychippus isonesus / PLATE 18. SUPERIOR AND INFERIOR MOLAR TOOTH TYPE OF MERYCHIPPUS. PA ess CONSTRUCTION OF TEETH IN MERYCHIPPUS. COMPARATIVE VIEWS OF TYPICAL UPPER PREMOLAR, Pt, AND LOWER MOLAR, Me, IN DIFFERENT SPECIES. FROM TEETH PRE- FORMED IN THE JAW BEFORE ERUPTION AND DEPOSITION OF CEMENT. All figures natural size. Left column. Pawnee Creek, Col. Middle Miocene 1. Merychippus paniensis Cope, referred specimen, Am. Mus. 9422. ce, Anterior view, 5, internal view. Snake Creek, Sioux ?Lower Pliocene 2. M. calamarius Cope, referred specimen, Am. Mus. 14014. a, External view, Co., Nebr. b, internal view, c, anterior view, d, posterior view. Right column. Sheep Creek, Neb. Middle Miocene 3. WM. tsonesus primus Osborn, type, Am. Mus. 14187 (reversed in drawing). Pawnee Creek, Col. rs is 4. M. sphenodus Cope, referred specimen, Am. Mus. 9408. e ct is a 5. M. paniensis, referred specimen, Am. Mus. 8255. Snake Creek, Sioux Lower Pliocene 6. M. calamarius Cope, referred specimen, Am. Mus. 1390la. a, External Co., Nebr. view, , internal view, c, anterior view, d, posterior view. Note the marked progression in the length of the molar crowns and the size of the molar teeth exhibited in the lower grinding tooth of M. isonesus primus Osborn (Fig. 3) and the corresponding tooth of M. calamarius Cope (Fig. 6). 258 Memoirs Am. Mus. Nat. Hist. N.58., Vol. II, Plate 18. IS \ : sphenodus Iw Merychippus isonesus primus “? % Laer, Merychippus pantensis es Dang Boge ' LOWER TEETH, MERYCHIPPUS. PATH 182 LOWER TEETH OF MERYCHIPPUS FROM NORTHEASTERN COLORADO. COMPARISON OF THE TEETH AT DIFFERENT STAGES OF WEAR IN TWO SPECIES FROM THE MIDDLE MIOCENE OF COLORADO. THE UPPER TEETH OF THE SAME INDIVIDUALS ARE FIGURED ON PLATES 15, 16. All figures natural size. Pawnee Creek, Col. Middle Miocene 1. Merychippus sejunctus Cope, referred specimen, Am. Mus. 8273. Teeth little worn. i . a . 2. M. sejunctus Cope, type, Am. Mus. 8291. Teeth well worn. e us a ; < 3. M. campestris Gidley, type, Am. Mus. 9096. Teeth little worn. (Drawn from left lower series reversed, the right ramus being diseased.) : : sh ss . 4, M. campestris Gidley, referred specimen, Am. Mus. 9459. Teeth much worn. 260 Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 19. Merychippus sejunclus Merychippus sejunclus Merychippus c ampestris BS LM. Merychippus campesiris PLATE. 20. x SKULL AND LOWER TEETH, MERYCHIPPUS. POAT He2 0: SKULL AND LOWER TEETH OF MERYCHIPPUS FROM NORTHEASTERN COLORADO. COMPARISON OF THE OUTER AND CROWN VIEWS OF THE TEETH OF FOUR SPECIES FROM COLORADO. The limbs and feet of these skeletons are compared on Plates 44, 47, 49, and the upper teeth of M. proparvulus from another specimen on Plate 15, also feet, Plate 54. Skull one-half natural size. Teeth natural size. Pawnee Creek Middle to Up- Merychippus sejunctus, type skull, Am. Mus. 8291. per Miocene 7 : ie 1. M. eoplacidus Osborn, type, Am. Mus. 9397. Teeth little worn. bo M. eohipparion Osborn, type, Am. Mus. 9402. Teeth almost unworn, ms; not fully erupted. 3. M. proparvulus Osborn, paratype, Am. Mus. 9398. Teeth about half worn. ae Memoirs Am. Mus. Nat. Hist. N.8., Vol. II, Plate 20. * * x x \ ry ‘ S y \ Oa (A y a TO /Vo.829/ Type As JX), ihe IVO. 93297 Type A. /7. CLI GI CIC CEC! a 1 ZX ZS 3 eee pee NN ea i Merychippus eoplacidus Wo i fh } Meryc hippus eohipparion NO. 9398 (Paratype) A. #4. eas Line | Merychippus proparvulus PLATE 2. FACE, PROTOHIPPUS. 263 PLATE 21. PREORBITAL FOSSA IN PROTOHIPPUS. COMPARISON OF FACIAL PART OF SKULL IN THREE SPECIES FROM THE UPPER MIOCENE OF NEBRASKA AND SOUTH DAKOTA. All figures one-half natural size. Little White River, So. Dak. Lower Pliocene 1. Protohippus simus Gidley, type, Am. Mus. 9820. Lachrymal fossa shallow; no malar fossa. Niobrara River, Nebraska “ é 2. P. niobrarensis Gidley, type, Am. Mus. 10828. Lachrymal fossa restricted, moderately deep, anterior in position; no malar fossa. Little White River, So. Dak. os 3. P. perditus Leidy, neotype (Gidley), Am. Mus. 10838. Juvenile skull; lachrymal fossa restricted, rather shallow; no malar fossa. Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 21. Protohippus simus Protohippus niobrarensis NO. /0G38 MVeotype AST. a Lng. Profohippus perditus PLATE 22. £ TYPE TEETH, PROTOHIPPUS. PLATE 22. TYPES OF THREE SPECIES OF PROTOHIPPUS. All figures natural size. Republican River, Driftwood Creek, Nebr. Lower Piscean Little White River, So. Dak. a portion of the upper jaw conan all the Tange cheek teeth except m!. i: Republican River, Nebr. _ . BP. profectus Cope, type, Am. Mus. 8349. six . superior molar teeth of the left side. | Memoirs Am. Mus. Nat. Hist. N.S., Vol. II, Plate 22. uA TEA23. ? FACE, PROTOHIPPUS, PLIOHIPPUS. PLATE 23. SKULLS OF PROTOHIPPUS AND PLIOHIPPUS FROM THE UPPER MIOCENE OF TEXAS. All figures one-half natural size. Llano Estacado, Texas Lower Pliocene 1, la. Pliohippus fossulatus Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14395). Lachrymal and malar fossee moderately deep, anterior in position, excavation continuing forward below nasals and premaxille. 1 Side view, la superior view of same skull, showing undercutting below nasals and premaxille. 2. Protohippus pachyops Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14394). Lachrymal fossa anterior in position, restricted, rather deep; no malar fossa. The generic and specific reference of  Mus. Nat. Hist. , BO \\\ | IW [A 7y pe Lae AN A WY Une v. 5 x ‘g SY — 5 ~ wo S » S= | 3 Y, a : SF = i 7exas N eS x g S pac hyops Protohippus LAL a 1d Gente | -S im. - 2 ey Tee a) TEETH, PROTOHIPPUS, PLIOHIPPUS. PLATE 24. TEETH OF PROTOHIPPUS AND PLIOHIPPUS FROM NORTHERN TEXAS. TYPE SPECIMENS FROM THE CLARENDON AND BLANCO BEDS OF TEXAS OF SPECIES DESCRIBED BY BE. D. COPE IN 1892-3. Texas All figures natural size. Lower Pliocene 1. Pliohippus fossulatus Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14395), Middle p*-m’, moderately worn. a, External view, c, anterior view. - 2,2a. Protohippus pachyops Cope, Univ. of Texas Coll. (cast Am. Mus. 143894), upper and lower milk dentition of type skull, dp’-m?, dpy-me, moderately worn. € 3,4. Pliohippus cumminsii Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14393), upper molars, 3, 4, crown and, d, posterior views. - 5. Pliohippus simplicidens Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14388), upper molar. a, External, c, anterior, and crown views. < 6. Pliohippus interpolatus Cope, type, Univ. of Texas Coll. (cast Am. Mus. 14387), m?. d, posterior, a, external and crown views. 270 Memoirs Am. Mus. Nat. Hist. N.8., Vol. II, Plate 24. LI = y SS SS. ae! KS : > 4 | : med i yl Pliohippus fossulatus Type, Univ. Tex. Byes 4 1 Pliohippus simplicidens Type, Unyv. Tex ht P liohip pus cumminsii Pliohippus inter polatus Pr AiE 5. _ MILK TEETH, PARAHIPPUS — HIPPARION. Pee Aer e27o% UPPER MILK TEETH OF PARAHIPPUS, MERYCHIPPUS, PROTOHIPPUS, PLIOHIPPUS, AND HIPPARION. DECIDUOUS PREMOLARS IN DIFFERENT SPECIES OF PARAHIPPUS, MERYCHIPPUS, PROTOHIPPUS, HIPPARION, AND PLIOHIPPUS. Pine Ridge, So. Dak. Niobrara River, Nebr. Bijou Hills, Missouri River, Sheep Creek, Sioux Co., Nebr. Pawnee Creek, Col. Snake Creek, Nebr. Upper Pawnee Creek, Col. Little White River, So. Dak. Niobrara River, Nebr. Little White River, So. Dak. Lower “ Lower Sheep Creek, Sioux Co., Nebr. “ Miocene Pliocene Pliocene All figures natural size. wo ) | NI Parahippus pristinus Osborn, referred specimen, Am. Mus. 12915. Primitive stage of Parahippus. Parahippus cognatus Leidy, type, drawn from cast Am. Mus. 10772. Progressive stage of Parahippus. Merychippus insignis Leidy, type, dp?, (drawn from cast Am. Mus. 10770, reversed in drawing). Early stage of Merychippus. Merychippus isonesus primus Osborn, referred specimen, Am. Mus. 14187d. Earliest stage of Merychippus. 