FOSSIL REPTILES. 211 



pass through the two sides of the osseous vertical plate of the 

 sphenoid. The nerves of the third and fourth pair, and the 

 first branch of the fifth, pass through particular foramina (be- 

 fore mentioned) of the temporal alae. Those of the sixth 

 through a canal of the body of the sphenoid. 



This vertical lamina in front of the lodgement of the pitui- 

 tary gland evidently corresponds to a part of the anterior 

 sphenoid in the mammalia, which, in the same manner, as- 

 sumes the form of a vertical lamina in the species whose inter- 

 orbital partition is slender, such as the sdimiri and the mush. 

 At the same time it is clear that there is no particular orbital 

 wing, since the nerves which, in the mammalia, pass through 

 the spheno-orbital cleft or foramen, or in other words, through 

 the interval of the orbital and temporal wings, pass here through 

 particular foramina in the temporal wing ; and also, that the 

 optic nerve, the essential function of whose orbital wing is to 

 surround its passage, passes into a foramen of the membrane, 

 or of the cartilage. 



In the foetus, indeed, a small point of ossification has 

 been found above the place through which the optic nerve 

 passes, which, however, is soon enveloped in the growth of the 

 temporal wing. This is the only vestige of an orbital wing in 

 the crocodile ; but it by no means fulfils the functions of that 

 process, for it is not between it and the rest of the temporal 

 wing that the nerves of the spheno-orbital foramen pass. 



It is only in the small vertical lamina that we might look 

 for an osseous representation of the anterior sphenoid; but no 

 suture is to be found distinguishing this lamina from the rest 

 of the sphenoid. 



To complete what relates to the sphenoid, we must speak of a 

 bone common to almost all reptiles, but which is never found 

 separate, either in the mammifera or birds. This is a large bone 

 with three branches, which proceeds from the as pterygoidevm, 

 or its internal apophysis, to the union of the jugal, the maxil- 

 lary, and the posterior frontal bones. This, says the Baron, if 



P 2 



