THE SKELETON OF THE VERTEBRATE HEAD. 131 



common orbital floor, and to support the cartilaginous bar-like 

 centrum of the pre-sphenoid, passes down as the osseous septum 

 of the posterior nares, and terminates in the form of a penta- 

 gonal plate in the palate, between the palatines and maxillaries, 

 and in some species in a hexagonal form, between the palatines, 

 the maxillaries, and intermaxillaries. The relations of the 

 ethmoidal neurapophyses to their meta-neurapophyses in the 

 bird, and the presence of the former in the maxillary 

 region of the palate, led me to suspect that the so-called 

 " vomer " of the turtle is the combined neurapophyses of its 

 ethmoidal sclerotome. But its posterior horizontal laminar 

 process which supports the cartilaginous pre-sphenoidal cen- 

 trum, as well as the process which forms the septum of the 

 posterior nares, indicated the probability of the " vomer " being 

 a still more complex bone. I have not met with the palatal 

 plate as a separate bone in the turtle, although in longitudinal 

 sections I have observed faint indications of its having been 

 so. I find, however, that in certain tortoises, not only is the 

 palatal plate connected by a distinct suture to the upper 

 portion of the so-called " vomer," but it is divided by a similar 

 suture in the mesial line of the palate into two halves. In 

 these tortoises, therefore, the separation of the posterior nares, 

 the junction of the descending processes of the ethmoido- 

 frontals, and the support of the cartilaginous bar-like centrum 

 of the pre-sphenoid, are affected by a distinct bone, which, 

 including its connections to the palatines, presents all the 

 characters of the so-called " vorner " of the bird. But I have 

 already stated my belief that the bone so-called is not the 

 vomer of the bird ; and in the sequel I shall state the grounds 

 on which I hold it to be the combined ento-pterygoids the 

 upper elements of the palatine arch. 



JEthmoidal Sclerotome in the Crocodiles. In the crocodiles 

 proper, and the gavials, the lachrymal is interposed between 

 the so-called pre-frontal and the maxillary. In the alligators 



