    Sentence 1: Which species are ribbon-shaped  planktonic animals?    Sentence 2: There are two known species, with  worldwide distribution _in_warm,_and_warm-  ‘temperate waters: Cestum veneris ("Venus’  girdle’) is among the largest ctenophores - up  to 1.5 meters (4.9 ft) long, and can undulate    slowly or quite rapidly.    