374 FOSSIL REPTILES. 



motion. They are all a little flatted, truncated, and dilated at 

 the ends, and ^narrowed in the middle. The last terminate 

 in an obtuse point. 



In this individual, which furnished the skeleton of Lyme, the 

 anterior limb, taken from the head of the humerus to the end 

 of the longest toe, was nearly twenty-three inches long. The 

 hinder limb was two feet. Thus they exceeded, a little, one- 

 sixth of the total length. 



These forms and proportions were confirmed by a less com- 

 plete skeleton, discovered at Lyme, by Captain Waring. 



The head is that part of the plesiosaurus which is least 

 known. 



The muzzle of moderate length, the form of the parietal, 

 the disposition of the bones which surround the orbit, and 

 the temporal foss, exhibit analogies with the iguana. But the 

 teeth adhere in distinct alveoli, as in the crocodile, and Mr. 

 Conybeare thinks that the nostril is near the anterior edge of 

 the orbit, as in the ichthyosaurus. 



In a fragment of muzzle presented to M. Cuvier, by Dr. 

 Buckland, there is no trace of nasal aperture. It would ap- 

 pear, therefore, that in these two genera of reptiles, the ichthyo- 

 saurus and plesiosaurus, as in the cetacea, to which they ap- 

 proximate in so many other respects, the nostrils were situated 

 towards the summit of the head. 



The teeth of the plesiosaurus are slender, pointed, arched a 

 little, and longitudinally channelled. They are unequal. The 

 anterior below, and the posterior above, are longer and thicke^ 

 than the others. It is not easy to determine the number of 

 the upper teeth, in consequence of the state of the materials, 

 but in entire dentary bones of the lower jaw, on each side, 

 twenty-seven alveoli were distinctly visible. The first six on 

 each side are the largest, and in this part, which makes nearly 

 the third of the length of the bone, the jaw is somewhat 

 swelled out. These dentary bones were far larger than those 

 of the Lyme skeleton, and are referred, by M. Cuvier, to an 



