32 ON THE PHYSIOGNOMY OF SERPENTS. 



cipital foramen are the largest. The entrance to that 

 cavity is protected above by an osseous plate like a scale, 

 salient and vaulted ; below projects the occipital condyle, 

 supported by a neck, and composed of three pieces, which 

 become one by age, forming a single plane, sometimes in 

 the form of a trefoil, sometimes of a heart. 



5. We come, finally, to the temporals^ all around im- 

 bedded between the occipitals and the parietals, and con- 

 taining in their cavities the organs of hearing ; the back 

 part contains the pars petrosa. 



The assemblage of the bones of the face are in the same 

 plane with those that form the bony case of the true cra- 

 nium ; and we sliall now describe them. We observe, first, 

 the anterior frontals, a pair of bones usually triangular, 

 which determine the lateral portions of the face, and by 

 their posterior portions assist in forming the anterior part 

 of the orbit ; the inferior surface of this bone extends to the 

 maxillary, with whicli it is articulated in the true venom- 

 ous snakes ; its form and its direction vary exceedingly, 

 according to the functions it has to perform, and its volume 

 is reduced in the latter class of animals to a very small 

 size. Finally, the internal surface composes the back part 

 of the nasal cavity, of which, however, the principal part 

 is formed by several bones attached by ligaments to the 

 cranium, and allowing a certain degi'ce of motion in a ver- 

 tical direction. The pieces which also form the base of 

 the snout, receive at this anterior end the intermaxillary : 

 They are, 1st, the vomer, composed of two symmetrical 

 pieces, united by their mtemal faces, broad and triangular 

 before, slender towards the extremity which unites them to 

 the sphenoid ; 2d, the nasals, almost always triangular, and 

 with an anterior plate descending to form the septum which 

 divides the nostrils ; they cover the nasal cavity ; 3d, a 

 small bone analogous to the turbinated bones. 



We perceive, moreover, in the skull of Ophidians several 

 supernumerary pieces, which, however, by no means occur 

 in every species. The first are the posterior frontals, bones 

 which descend from the summit of the front to defend the 

 posterior border of the eye. In the Trigonocephalus, the 

 Crotalus, and in some serpents not venomous, we find only 



