THE SKFI.KTON oF TIIK VKKTKl'.ItATH HEAD. 135 



disarticulating the skull of the crocodile the pteryj^oids 

 generally remain attached to the i)Ost-si)hcnoidal centiiim, so 

 that the prolonged anterior processes of the former present 

 the appearance of bemg elongations- of the latter, -wlach they 

 in fact are not. 



From the foregoing considerations, and on gi-ounds to be 

 explained in the sequel, when the palatine arch or hiemal arch 

 of the pre-sphenoidal sclerotome comes to be examined, I recog- 

 nise in the crocodilian vomer of Cuvier and Owen the proximal 

 or upper element of the pre-sphenoidal ha-mal arch — the same 

 element to which, when existing in certain fishes. Professor 

 Owen applies the sufliciently expressive term ento-pteiygoid. 



It will now be observed, that in consequence of the great 

 development of the pteiygoids, and of the ento-pterygoids in 

 the crocodilian, the latter, extending forward into the neural 

 space of the ethmoidal sclerotome, roof over the greater part, 

 and provide a septum for nearly the whole of that extent of 

 the nasal fossi\% the sides and floors of which are formed by 

 the so-called " palatals" or ethmoidal neurapophyses, and abut 

 against the descending processes of the " pre-froutals" or 

 ethmoido-frontals, without entirely extruding the neurapo- 

 physes from these processes, as in the chelonian. There is 

 another minor difference between these parts in the croco- 

 dilian and chelonian. In the chelonian, as has been already 

 stated, the ento-pterygoids having pushed the ethmoidid neu- 

 rapophyses from their natural connection with the descending 

 processes of the ethmoido-frontals, complete, by means of their 

 ascending divergent processes, the triangidar space for the 

 olfactory nerves. In the crocodilian, again, the descemling 

 processes of the ethmoido-frontals complete the space for the 

 olfactoiy neiTes, by means of a short process from each of 

 them, which, passing inwards, meets its fellow of the opposite 

 side a little above the junctions of the descending processes 

 themselves with the ento-pterygoids. The space left betwi'cn 



