258 FOSSIL REPTILES. 



back. Its external edge recurves with the neighbouring portion 

 of the jugal, and thus forms, in the lower part of the temple, a 

 sort of canal which commences at the foramen of communica- 

 tion of the temple with the orbit. Its posterior angle, on the 

 contrary, is directed a little towards the bottom, descending more 

 than the articulary facet for the lower jaw, and leaving between 

 it and the raised portion of the external edge a broad emargi- 

 nation. Between this angle and the articulary facet is a foss 

 hollowed in the tympanal, the sphenoid, and pterygoidean bones. 

 The mastoid tubercles are depressed, very salient behind, 

 and pointed. Their point is formed one-half by the mastoidean 

 bone, and the external occipital. The sphenoid shows itself 

 underneath on a wider surface than in the land-tortoises, and 

 the basilary appears there less. The lateral occipitals are also 

 very small, and speedily are soldered with the basilary. The 

 tubercle for the articulation of the atlas projects less than the 

 mastoidean apophyses. 



In the emys serpentina, at a certain age, no external occi- 

 pital is found distinct. It is united to the lateral occipital, but 

 in the land-tortoises to the upper occipital. The head is de- 

 pressed in front, the muzzle very short ; the orbits moderate, 

 and approximating to the muzzle ; the temple covered only at 

 its anterior portion by a lamina of the parietal, less com[)lete 

 than in the sea-tortoises, and by a widening of the posterior 

 frontal and of the jugal. The palatines have no palatine lamina : 

 the palatine and pterygoidean region is very flat. The foramina 

 analogous to the pterygo-palatines are very large, and the passage 

 of the auditory osseletis made by a foramen, and not a scissure. 

 In the Trionyx, or soft tortoises, the head is depressed, and 

 elongated behind. The muzzle in certain species, as in that of 

 the Nile, is pointed, short and rounded in others. The inter- 

 maxillaries are very small, and have no nasal or palatine apo- 

 physes. Behind them is a large incisive foramen. The maxil- 

 laries unite between them in the palate on a tolerably long 

 space, so that the back-nostrils are further back than in the 



