248 THE OSTEOLOGY OF THE REPTn.ES 



B. SUBORDER PLESIOSAURIA 



Marine reptiles from eight to about fifty feet in length, with 

 paddle-like, hyperphalangic limbs. Skull moderately broad to very 

 slender. Nares small, situated remote from the extremity and near 

 the orbits. Orbits with sclerotic plates. No distinct nasals. Internal 

 nares small, situated in front of the external. A pair of posterior in- 

 terpterygoidal openings divided by the parasphenoid always present; 

 other openings variable on the palate. The squamosals meet in the 

 middle line posteriorly. Coracoids very large, contiguous in midline; 

 clavicles and interclavicle small, sometimes vestigial. Ilium rod-like, 

 articulating below with ischium only, above with a well-developed 

 sacrum of three or four vertebrae. 



An extensive and long-lived group of purely marine reptiles, 

 widely distributed over the earth; as a whole clearly defined, but 

 with many minor modifications. The neck was extremely variable 

 in length, with from thirteen to seventy-six cervical vertebrae. The 

 body was broad, though not nearly so broad as represented in most 

 modern restorations. The most perfect specimen known — and the 

 author has seen most of them in the collections of the world — is that 

 of Thaumatosaurus victor, in the Stuttgart museum, of which a figure 

 copied from a photograph is reproduced here. The body, it is seen, 

 is broadly oval, but not flat, protected below by the extraordinary 

 developments of the pectoral and pelvic girdles and intervening 

 parasternal ribs. Their phylogenetic relationships with the Notho- 

 sauria are incontestable, though the closed palate of the latter indi- 

 cates that no known form could have been actually ancestral to 

 them. 



Family Plesiosauridae. Skull moderately long. From thirty- 

 five to [seventy-six] cervical vertebrae, the cervical ribs double- 

 headed. Scapulae not contiguous in the middle; no interclavicular 

 foramen; epipodials much longer than broad, no accessory epipo- 

 dials. Coracoids contiguous throughout. 



Jurassic. Plesiosaurus Conybeare, Thaumatosaurus Meyer, Europe. 



Family Pliosauridae. Skull long, neck short, composed of about 

 nineteen vertebrae. Cervical ribs double-headed; five pectoral and 

 about twenty dorsal vertebrae. Premaxillae continuous to parietals 

 in middle. Scapulae closely approximate in midline; coracoids con- 



