ON THE VERTEBRATE SKELETON. 251 
To the question why I should have invented new names when Geoffroy St. 
‘Hilaire had already proposed others for the vertebral elements, I can only re- 
peat the regret with which I found myself compelled to that invidious step, 
after having arrived at the conviction, that the learned Parisian Professor had 
sometimes applied the same term to two distinct elements, and sometimes 
two distinct names to one and the same element: and I am glad to be able to 
cite the authority of Cuvier for the propriety and advantage of such a step. 
His words are in reference to an analogous case, ‘‘ Donner a un mot connu un 
sens nouveau est toujours un procédé dangereux, et, si l’on avoit besoin 
d’exprimer une idée nouvelle, il vaudroit encore mieux inventer un nouveau 
terme, que d’en détourner ainsi un ancien *.” Now there is scarcely one term 
in the first column in Table II. which is synonymous with its opposite in the 
second column, or which expresses exactly the same idea; and the discrepancy 
becomes greater in regard to the terms applied to the vertebral elements of the 
head, in columns 1 and 5 of TableIII. The respective concordance of the views 
of the vertebral archetype entertained by Geoffroy and myself with Nature will 
be determined and judged of by succeeding impartial and original observers. 
With regard to the term cycléal, ‘de xvxdos, cercle, pour rappeler sa 
forme annulaire, permanentes chez les premiers,” (Articulata, Dermoverte- 
brés, Geoff.) “et, au contraire, non persévérante chez les derniers” (Verte- 
brata, Hauts-vertébrés, Geoff.), it is understood by its author to apply to the 
annular segment of the crust of the insect, as well as to the ‘centrum’ of the 
endoskeletal vertebra. Geoffroy’s primary division of the parts of a vertebra 
is into the centre or nucleus (noyau) and the lateral branches. The upper 
‘ branches laterales’ or ‘ périaux’ are equivalent to my neurapophyses and 
also to my neural spine, in fishes : the lower lateral branches or ‘ paraaux’ are 
sometimes free and floating+, when they answer to my ‘pleurapophyses’; 
but they are sometimes so united as to form a canal, when they answer 
to my ‘ parapophyses’ in the tail of fishes t, and to my ‘hamapophyses’ in 
the tail of cetaceans. Geoffroy supposed, for example, that the hemal canal 
in the tail in all fishes was formed by the ribs, bent down and anchylosed 
at both ends§, and that the hemal canal in the tail of the crocodile and 
whale was constituted by a like metamorphosis of the same vertebral elements. 
He, also, argued that, as the small spinal chord of fishes did not demand 
so great a development in breadth of the neurapophyses, they were permitted 
to attain to unusual length; and that, coalescing together, they thus consti- 
tuted not only the neural arch but the neural spine, to which latter, therefore, 
he extended the name ‘ périal’; whilst to the corresponding: part in mammals 
he gives the name of ‘épial’. But, again, in fishes, he calls the dermal 
spines developed in the embryonic median fold of integument which is meta- 
morphosed into the dorsal fins, ‘épiaux’ ; and the corresponding dermal spines 
of the ventral fin ‘ cataaux.’ The lepidosiren, however, manifests the neural 
spine distinct from both the neurapophyses below and the dermo-neural spine 
above: and such neural spine is unequivocally homologous with the anchy- 
losed neural spine in osseous fishes ||. It is quite in harmony with the position 
of the class of fishes at the bottom of the vertebrate scale that they should 
present a greater degree of calcification of the parts belonging to the same 
category of the skeletal system as the shells and crusts of the invertebrates : 
hence it is that whilst the median dermal fins of the marine mammalia have 
* Mémoires du Muséum, t. xx. p. 123. 
+ As they are illustrated in the abdominal vertebra of the fish figured by Geoffroy in the 
‘Mémoires du Muséun,’ t. ix. (1822), pl. 5, fig. 4, o. t Jb. fig. 2,0 0. 
§ This occurs as an exceptional condition, in the lepidosteus, and perhaps in lepidosiren. 
|| Linn. Trans, vol. xviii. p. 23, fig. 4, ¢, d. 
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