396 CRETACEOUS REPTILES. 
Order CHELONIA. 
Family Marina. 
Genus Cuetone. (Tab. XXXIX. figs. 5 & 6.) 
Of several fragmentary specimens of fossil remains from the chalk, referable 
to the Chelonian order, in the Museum of Mr. Dixon, the most characteristic is 
the series of five marginal plates represented of the natural size at figures 5 & 6, 
Tab. XXXIX,. The inner surface of these plates being excavated by the cavities 
for receiving the pointed ends of the ribs, as shown in figure 5, such indication 
of that articulation by gomphosis enables one to refer the specimens to a large 
species of Turtle (Chelone). 
Order ENALIOSAURIA. 
Family PLestosauroIpEa. 
Genus PLEsIosauRUS. 
Of all existing Reptiles the Chelonians make the nearest approach to the pre- 
sent remarkable extinct genus in the length and flexibility of the neck, in the 
size of the true body of the atlas (processus dentatus, Auct.), which resumes its 
normal relations with the neural arch of that vertebra in Chelys and Chelodina ; 
in the natatory form of the extremities as exemplified in the paddles of the 
Turtle ; and in the great expanse of the ischium and pubis; whilst the Plesio- 
sauri exhibit, next to the Turtles, the greatest development of the abdominal 
ribs (heemapophyses and their spines), which form a kind of interwoven flexible 
‘plastron’ beneath the abdomen. I pass therefore in the present catalogue of 
British Reptilian Fossils from the aquatic Turtles to the extinct marine Saurians. 
Species. Plesiosaurus Bernardi, Owen. (Tab. XL.) 
In my ‘ Report on British Fossil Reptiles,’ one species of Plesiosaurus, viz. 
Plesiosaurus pachyomus, was defined from remains discovered in the greensand 
division of the Cretaceous series * ; and the existence of the genus Plesiosaurus, 
at the period of the deposition of the latest member of that series, was inferred 
from the discovery of the femur of a large species in the chaik which forms the 
well-known ‘ Shakespeare’s Cliff’ near Dover f. 
* «Report on British Fossil Reptiles,’ Trans. Brit. Association (1839), p. 74. + Ibid. p. 193. 
