tiguous throughout. Two or three epipodials, as broad as long or broader. Ischia long. Large or very large.
Jurassic. Pliosaurus Owen, Peloneustes Lydekker, Europe.
Family Cryptocleididae. Very much like the following family, but the neck is shorter, with from thirty-two to forty-four vertebrae; and the coracoids are contiguous throughout. From two to four epipodials, all short. Cervical ribs single-headed. Skull short.
Jurassic. Cryptocleidus Seeley, Muraenosaurus Seeley, Tricleidus Andrews, Picrocleidus Andrews, Microcleidus Watson, Sthenarosaurus Watson, Europe.
Fig. 174. Skeleton of Trinacromerum osborni, a Cretaceous plesiosaur, as mounted in the University of Kansas Museum.
Family Elasmosauridae. Head short, neck very long, with from more than fifty to seventy-six vertebrae; ribs single-headed. The scapulae meet in midline; no interclavicular foramen. Coracoids broadly separated on their posterior half. Ischia short. Two epipodials only, short.
Upper Cretaceous. Elasmosaurus Cope, Ogmodeirus Williston and Moodie, Leurospondylus Brown, North America.
Family Polycotylidae. Skull very slender. Premaxillae articulating with parietals. Neck not longer than head, with from twenty-three to twenty-six vertebrae; ribs single-headed. The precoracoidal process separates the scapulae in the midline; an interclavicular foramen; coracoids contiguous throughout. Ischia elongate. Three or four epipodials, all short.
Upper Cretaceous. Polycotylus Cope, Trinacromerum Cragin, ? Piratosaurus Leidy, North America.
