ON THE VERTEBRATE SKELETON. 319 
_. Cuvier affirms, however, in support of his argument, that, although the 
orbitosphenoids are never separated from the frontals, as the alisphenoids are 
from the parietals, in the mammalia, they are almost always separated from 
the frontals in the other classes, so that the vertebral ring is again inter- 
rupted *. But, were even the frontals commonly uplifted above the orbito- 
sphenoids in birds, reptiles and fishes, which does not accord with my ex- 
perience, the objection, on that score, to regarding them as ‘neural spines,’ 
would as little apply, as it does to the universally recognised general homology 
of the separated and uplifted neural arch of the first vertebra of the trunk 
of the Ephippus and some other fishes. 
Cuvier finally regards the connection of the frontals with the prefrontals, 
which he calls ‘ ethmoid’ in mammals, ‘l’enchdssement de l’ethmoide,’ as a 
function quite remote from any of a vertebral character, “ relative 4 toute 
autre chose.” This objection only shows the necessity of a right apprecia- 
tion of special homologies, in order to form a true judgement respecting 
general homology ; and, with respect to the ‘ ethmoide,’ I must refer to the 
section on the prefrontals in the chapter on ‘ Special Homology (p.214). If 
the arguments there adduced be held to prove the crista galli and cribriform 
plate in the human skull to be the homologues of portions of the coalesced 
prefrontals and olfactory capsules, we may next remark that these portions 
are not merely wedged between the orbital plates of the frontal, but articu- 
late behind by a persistent suture with the orbitosphenoids. As neurapo- 
physes, the coalesced prefrontals of the terminal vertebra of the skull thus 
articulate with their next succeeding homotypes; and, by virtue of the ex- 
cessive development of the spine of the frontal vertebra, as well as from their 
being contracted and drawn backward in the human skull, they articulate 
with such spine (the frontal) as well as with that of their own proper seg- 
ment (the nasals). But, in the crocodile (fig. 9), we have seen a similar 
relation manifested not only by the more normal neurapophyses (14) of the 
nasal vertebra, but likewise by those (10) of the frontal, those (6) of the 
parietal, and those (2) of the occipital vertebra. 
All the objections raised by Cuvier to the general homology of the cranial 
bones as modified vertebral elements, equally apply to elements of vertebree 
in the trunk, which Cuvier himself has admitted to be vertebra, notwith- 
standing such modifications. The repetition of the perforated character of 
the human alisphenoid and orbitosphenoid in the neurapophyses of the trunk- 
vertebrze of many inferior animals, requires only a passing notice. The 
flattening, expansion and sutural union of the human supraoccipital, parietal 
and frontal bones, are matched by the neural spines in the carapace of the 
tortoise. If the basioccipital, basisphenoid and presphenoid are broad and flat, 
instead of cylindrical, so likewise are the bodies of the sacral vertebre in the 
broad-bodied megatherioids and in many birds. If the basioccipital and 
basisphenoid are lengthened out and firmly united together by deeply in- 
dented sutural surfaces in most fishes, so likewise are the bodies of the four 
anterior vertebre of the trunk in the pipe-fish (fistularia). If the basi- 
sphenoid and presphenoid be developed each from two ossifie centres, as in 
man, so likewise may the body of the human atlas be ossified; and even should 
the moieties of that centrum not coalesce at the median plane, they would 
» * “Ce que j’ai dit des pariétaux s’applique aux frontaux, considérés comme compléments du 
sphénoide antérieur ; leur fonction est relative 4 toute autre chose, la protection des lobes 
antérieurs du cerveau et 4 l’enchassement de l’ethmoide; et quoique le sphénoide antérieur 
n’en soit jamais séparé dans les mammiféres comme le postérieur l’est souvent des pariétaux, 
il Pest presque toujours dans les autres classes, en sorte qu’alors V’anneau vertébral serait 
aussi interrompu.”—/. c. p. 714. 
