350 



PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



confluent at the base. The dorsal vertebrae are distinguished 

 by the correspondingly great development of the transverse 

 processes upon the neurapophyses." x 



Top of the Cases, Specimens of Plesiosaurus Arcuatus. 

 WALL-CASE E. [5.] WALL-CASE F. [6.] 



PLESIOSAURUS MACROCEPHALUS. Wall-case E. A fine 

 skeleton, between four and five feet in length, from Lyme 

 Kegis, discovered and developed by the late Miss Mary 

 Anning, was figured and described by Dr. Buckland under 

 the name of P. macrocephalus, from the relatively great size 

 of the cranium as compared with that of the typical P. doli- 

 chodeirus.2 A cast of this specimen was presented to the 

 British Museum, by that eminent and zealous palaeontologist, 

 the Earl of Enniskillen ; and the osteology of this species is 

 fully elucidated by Professor Owen. 3 



The arched position into which the vertebral column has 

 been thrown, presents the entire skeleton on a comparatively 

 small area. The upper part of the cranium, with the orbits, 

 and the jaws and teeth, are exposed. The cervical and dorsal 

 vertebrae form a continuous, and but slightly dislocated series : 

 the tail is imperfect ; the anterior and posterior paddles of the 

 left side are entire. 



The length of the neck exceeds that of the lower jaw only 

 twice, instead of thrice as in P. Hawkinsii. The greater de- 

 velopment of the head is associated with thicker and stronger 

 vertebrae ; there are twenty-nine in the cervical region ; the 



1 " Brit. Assoc. Rep." p. 75. 



2 Dr. Buckland's " Bridgewater Essay," PI. XIX. 



3 " Brit. Assoc. Reports," 1839, pp. 6269. 



