350 Structure of the Fossil Saw tans. 



and blood-vessels were distributed. The developement of the 

 teeth took place within ; and not by means of a lateral, but 

 a vertical, penetration of the middle. The compressed situ- 

 ation, and the sharp attrition of the sides of the teeth, indicate 

 that, when the mouth was closed, the teeth of the upper jaw 

 did not pass in between those of the lower jaw, but that one 

 row overlapped the other. All these characters distinguish 

 the Saurocephalus from the Ichthyosaurus and Plesiosaurus : 

 in many respects, this animal would rather resemble the Ich- 

 thyosaurus. 



Sau'rodon Hays* 

 Dr. Isaac Hays describes a portion of the head and lower 

 jaw of a fossil reptile which belongs to Isaac Lea. It is from 

 a marl-pit near Moorstown (New Jersey). In form, the 

 animal has some similarity to the Saurocephalus of Harlan. 

 The teeth, however, characterise it as a new genus. The 

 teeth touch each other throughout ; and within every alveolar 

 socket is a series of apertures for the passage of the vessels 

 and nerves of the teeth ; besides which, the lower row of teeth 

 go completely within the upper. As yet, one species only 

 has been found, which is named S. Leanus; the teeth are 

 sharp, pressed, and not bent at the point. 



Teleosau'rus Geo/. 

 The separation of Cuvier's Gavial of Caen had already 

 been undertaken by Geoffroy St. Hilaire.f Recently, however, 

 this writer has pursued some fresh investigations respecting 

 this animal, with the advantage of possessing more extensive 

 knowledge of the structure of the Saurians in general. The 

 bones which Geoffroy names the pterygoid are smaller in this 

 animal than in the Crocodile, and therefore present much 

 similarity to the Mammalia. This is the reason why the 

 canal of the palate in these animals is not so very much elon- 

 gated as in the Crocodiles, and opens at a point of the basis 

 of the skull placed much farther back ; while it is only the 

 shortness of the canal of the nose which, in the Teleosaurus, 

 reminds us of the organisation of the Mammalia : yet the 

 posterior region of the skull is of the Crocodilian type; 

 and, in the structure of the ear, the creature approaches 

 not only to most of the oviparous quadrupeds, but even 

 to the Birds. The os jugale, in its form and situation, 

 approaches more nearly to the Mammalia than to any reptile 

 whatever. The temporal bone, as well as the os jugale, lay 



* This is also a fish, the Saurocephalus Leanus of M. Agassiz. — Ed. 

 \ Mem. cm Mus., torn. xii. p. 124., with better plates than in the work of 

 Cuvier. 



