478 PLESIOSAURIA 



CHAP. 



nearly 5 feet long and 2 feet broad, armed with many enor- 

 mous conical teeth, some of whieli reach one foot in length, 

 inclusive of the long collar and root -portion. The neck is 

 rather short, owing to the mucli condensed, disc-shaped centra 

 of the vertebrae. Total length of tliis species about 30 feet. 

 Other species in England and continental Europe as farasEussia. 



Fam. 2. Plesiosauridae. — The neck is very long, and consists 

 of from twenty-eight tu forty vertebrae. The scapulae do not meet 

 ventrally, but the symphysial portion of the coracoids meets the 

 clavicles and the interclavicle, the pectoral arch thus enclosing 

 two foramina. Chief genus Plesiosauriis, with many species. The 

 head is comparatively small, the neok very long, the tail short, 

 although consisting of from thirty to forty vertebrae. The third 

 digit (Fig. 113,C) is the lougest,and possesses nineor ten phalanges. 

 The abdominal ribs are very strong, and reach from the pectoral to 

 the pelvic girdle. Eange from the Lower Trias to the Lower 

 Oolite, chiefly European. P. dolichodirus and P. conyheari, the 

 latter reaching a total length of more than 15 feet, from the 

 Lower Lias, especially at Lyme Kegis. 



Fam. 3. Elasmosauridae. — The neck is extremely long, posses- 

 sing from thirty-five to seventy-two vertebrae, with single-headed, 

 not bifurcated, ribs. The scapulae meet ventrally, and enclose with 

 the very broad coracoids two foramina. The tail is short. The 

 pisiform bone articulates w4th the humerus. Otherwise much re- 

 sembling the Plesiosauridae. Principal genus Cimoliasaurus, with 

 many synonyms, and many species from the Middle Oolite to the 

 Upper Chalk ; cosmopolitan distribution, e.g. C. caritahrigiensis, of 

 tlie Greensand and Upper Chalk ; C. truchantericus, of the Kim- 

 meridge clay ; C. liaasti in New Zealand ; C. australis, C. chilensis ; 

 others in North America. Cryjitoclidus of the Middle and Upper 

 Oolite of Europe. Ulasmosaurus, of the Upper Cretaceous forma- 

 tion in Kansas, with a computed total length of 45 feet, of which 

 22 belong to the neck, with its seventy-two vertebrae. 



Sub-Class VIII.—ICHTHYOSA URIA. 



3Tarine, vhcde-slia^ied reptiles, with the anterior and ^posterior 

 limhs transformed into hyperi^halangcal ixiddles. Restricted 

 to the Mesozoic age from the 2Vias to the Upper Chalk. 



The skull is long, owing to the elongated slender snout, which 



