THE SKELETON OF THE VERTEBRATE HEAD. 139 



neurapophyses. Its lower surface is supported by the two 

 triangular bones, covered with teeth, and which are the neura- 

 pophyseal ethmoidal elements, already examined in the other 

 Vertebrata, The posterior nares are situated behind, between 

 the outer margins of these so-called vomerine bones and the 

 maxillaries. The latter are, as usual, connected to the eth- 

 inoido-frontals. 



Of the Views which have been hitherto taken of the Ethmoidal 

 or Nasal Vertebra, or Sclerotome. I am precluded in an ab- 

 stract from entering upon the important but tangled morpho- 

 logical history of the nasal segment of the cranium. I shall 

 only, therefore, on this department of the subject, make a few 

 observations, in deference to the authority of Professor Owen, 

 and in explanation of those points on which I find myself at 

 variance with his doctrine. I have already so far stated, and 

 in the sequel shall more fully state, the grounds on which I 

 dissent from the doctrine of Oken and Bojanus, adopted by 

 Professor Owen, that the nasals and vomer are respectively 

 the neural spine and body of the nasal vertebra. What I in- 

 tend more particularly to notice at present is that part of Pro- 

 fessor Owen's doctrine which relates to the neurapophyseal 

 elements of the nasal vertebra. 



Professor Owen considers the middle plate of the mam- 

 malian ethmoid to be the coalesced pre-frontals, and the two 

 halves of the cribriform plate, the ethmoidal cellules, . and 

 turbinated laminse, to be collectively the greatly-developed 

 olfactory capsules. If the latter are kept out of view, as not 

 entering, according to his doctrine, into the formation of the 

 ethmoidal or nasal neural arch, the doctrine necessitates the 

 conversion of the laterally-placed "pre-frontals" of the fish 

 and reptile into a single mesial laminar bone. Here I would 

 observe that, overlooking for the present the adoption by Pro- 

 fessor Owen of the current statements as to the identity of 

 the "pre-frontals" of the fish with the "pre-frontals" of the 



