FOSSIL REPTILES. 207 



the mammifera. In the saimiri for example, and some of the 

 moschiy in which the interorbital partition is reduced to a 

 single lamina; it has membranous spaces. 



The bone above mentioned, placed between the lachrymal 

 and frontal, M. Cuvier first considered as a second lachrymal; 

 but a more attentive examination clearly proved it to be a 

 portion of the frontal bone, that which in man is named the 

 infernal orbital apophysis, or in the mammalia the antiorbital 

 apophysis, which here is constantly detached from the body of 

 the bone ; M. Cuvier names it the anterior frontal. 



It is sufficient to place the head of a mammiferous animal, of 

 a ruminant, for instance, by the side of the head of a crocodile, 

 to be assured that in the latter this dismemberment of the frontal 

 bone has taken place ; one might, without deranging anything, 

 design on the frontal of the mammiferous animal, the suture 

 which exists in the crocodile, and thus detach, in the first, an 

 anterior frontal which would have the same position, almost the 

 same figure, and absolutely the same office as in the crocodile. 



This theory is entirely confirmed by the observation of the 

 fresh head. There we see the frontal, conformably to its or- 

 dinary part, covering the anterior portion of the encephalon ; — 

 separating the orbits — giving a point of attachment to the 

 levator muscles of the eye — allowing the olfactory nerves to 

 pass under its part situated between the orbits. We find that 

 it is expressly between its two dismemberments, called anterior 

 frontals, that these nerves proceed from the cranium, after 

 having been swelled into ganglia, and divided into numerous 

 threads, — that these threads cross a cartilaginous sieve, placed 

 between the two anterior frontals, as in the mammifera is 

 placed the sieve -like plate of the ethmoid. We find that it is un- 

 der this sieve that the anfractuosities or cornets commence, over 

 which the pituitary membrane is spread, and where the threads 

 in question are distributed ; but that these cornets remain 

 cartilaginous like the sieve, and like the vertical lamina, 

 which separates the orbits under the passage of the olfac- 



