Till-: SKKLKTON OF TIIK VKUTKlUtATE 111:AI». 155 



splieuoido-froutals near tlieir lower extremities, and the con- 

 sequent space left between tliis bony bridge and the deep 

 furrow formed by the inclined upper surfaces of the ento- 

 ptery^goideal portions of the pteiygoids. 



In the Latrrtians. — In the lizards, the sphenoido-frontal 

 is again double. In consequence of the mesial separation of 

 the euto-pterygoids ("palatals") and pterj-goids, the elongated 

 fibro-cartilaginous centrum and neurapophyseal interorbital 

 laniiiifc, are left unsupported below ; to which circurustance 

 is probably due the formation in the interorbital laminae of a 

 pair of delicate triradial osseous neurapophyses, which pass 

 oif from the upper margins of the optic foramina. 



In the Ophidian and Batrachian. — Leaving the further 

 consideration of the special homology of the anterior sphenoidal 

 wing in the reptiles, and more especially in the crocodiles, 

 imtil the posterior sphenoidal wing, and the so-called "petrosal," 

 have been examined, I would observe, that the grounds on 

 wliich Professor Owen distinguishes the "os en ceinture" 

 of the frog, from that segment in the python wdiich includes 

 the so-called "frontals," appear to me somewhat arbitrary. 

 This segment in the serpent consists of a pair of neurapophyses, 

 or orbito-sphenoids, which are distinct, as cartilages at least, 

 in the embiyo ; of a double meta-neurapophysis (sphenoido- 

 frontals), which not only occupy on each side the positions of the 

 neurapophyses, but extend the fore part of their inner margins 

 downwards, back to back, in the mesial plane, on the sides of 

 the compressed centrum ; which thus, along with them, 

 divides the neural chamber in front, for the transmission of 

 the olfactoiy ner\'es. The sides of the " os en ceinture " are 

 formed by neurapophyses ; while the so-called " fi-ontals " of 

 the serpent occupy the gieater part at least of the sides of 

 their segment ; in other respects, their relations are similar. 

 They are both catacentric ; the centrinn, in both, resting, as 

 in the bird, on the up]>or surface of the anterior acuminated 



