KEPTILIA. 



51 



elongated and broad coracoid bones. The clavicle is united to the scapula, as 

 in Chelonia. Next to Turtles, the Plesiosaurus exhibits the greatest develop- 

 ment of abdominal ribs. The ribs are articulated as in Lizards. The digits 

 of the fore paddle support respectively 3, 5-7, 8 or 9, 8, and 5 or 6, phalanges; 

 those of the hind-paddle have 3, 5, 8 or 9, 8, and 6. The Plesiosaurus differs 

 from the Ichthyosaurus in being pentadactylous, in having a long neck, longer 

 ^nd more flexible paddles, a shorter tail, vertebrae longer and nearly flat, with 

 two pits on the under side, and more slender teeth. The latter is generally 

 found lying on the side; the former, extended on its back. The Plesiosaurus 

 dolichodeirus is characterized by its extremely long neck and very small head. 

 The proportion of the parts is nearly thus: taking the head as 1, the neck will 

 be 5, the body 4, and the tail 3; the whole length being thirteen times that of 

 the head. The four paddles are equal in size. The original of this specimen, 

 in the British Museum, was discovered in the Lias at Glastonbury, England. 



Size, 6 ft. X 3 ft. 9 in. 



No. 75. [327] Plesiosaurus macrocephalus, Conyb. 



Skeleton, on slab (cast). This species is distinguished by the relatively 

 larger size of the head and thicker neck. The neck is three times the length 



^^t 



of the head ; and the posterior paddles are longer than the anterior pair. In 

 this very perfect specimen, belonging to the Earl of Enniskillen, Ireland, the 

 vertebral column is thrown into an arched position; the cervicals and dorsals 

 form a continuous series; the tail is imperfect. Three paddles are exposed, 

 and the upper part of the cranium with the orbits and jaws and teeth are 

 clearly defined. The original was discovered in the Lias of Lyme-Regis, 

 England, by Miss Mary Anning, and described by Dr. Buckland. 



Size, 3 ft. 9 in. X 3 ft. 6 in. 



