an extensive division of pectinibranchiate gastropods, including those that have a long retractile proboscis, with the mouth at the end, as the cones, whelks, tritons, and cowries. see illust. of gastropoda, and of winkle.-a subdivision of the taenioglossate gastropods, including the fig-shells (pyrula), the helmet shells (cassis), the tritons, and allied genera.