154 PROFESSOR OWEN ON THE DEVELOPiVlENT AND HOMOLOGIES OF THE 
&c. (see the concluding memoir of tom. iv. 1812, p. 2). In the second edition of the 
‘ Ossemens Fossiles ’ (tom. v. pt. 2. 1824), Cuvier, after remarking “that the mar- 
ginal pieces do not correspond exactly to the vertebral ribs ; that the first of the 
dilated ribs forming the carapace joins the third of the marginal pieces ; and that 
the tenth does not receive any rib,” observes, in reference to the latter expression, 
“ ne regoit aucune cote Ce ne pourroit done etre aussi que sous un point de vue 
philosophique que Ton regarderoit les pieces marginales comme representant les car- 
tilages ou parties sternales des cotes. Toutefois, comme il y en a onze, ce qui est 
precisement le nombre des vertebres dorsales et lombaires, c’est un motif pour adopter 
ce point de vue. Les deux premieres et les deux dernieres servaient, comme on I’a dit 
en d’autres occasions, des cotes sternales auxquelles leurs cotes vertebrales manque- 
roient,” p. 200. In the posthumous edition of the ‘ Legons d’ Anatomic Comparee,’ 
Cuvier gives only grounds for rejecting, not any for adopting, the views of Geoffrov, 
in regard to the marginal pieces, and observes, “ On a considere ces pieces comme 
analogues aux portions sternales des cotes : il faut avouer au moins qu’elles ne leur 
repondent pas pour le nombre, et que dans les trionyx sur-tout, elles ne leur corre- 
spondent point pour la position. C’est a la troisieme ou a la quatrieme que com- 
mence leur engrenage avec les deux pieces moyennes du sternum ; il finit a la huitieme, 
mais dans les tortues de mer cette union n’a pas lieu.” Tom. i. 1835. 
Bojanus, who has given the most complete and masterly analysis of the emydian 
modification of the carapace and plastron, calls the neural plates ‘ processus spinosi 
vertebrarum dorsi,’ the costal plates ‘costse,’ and the bones of the plastron ^sternum:’ 
he offers no homology of the ‘marginal’ plates, but retains for them the absolute 
names of ‘ ossa marginalia*.’ 
The eminent physiologists and comparative anatomists of our own country have 
not, however, partaken of this reserve of the great French master of the science, or 
of the celebrated German monographer, towards the Geoffroyan hypothesis of the 
marginal pieces. Dr. Roget, in his ‘ Bridgewater Treatise,’ after a brief but clear 
summary of the general structure and uses of the carapace and plastron, says, “ We 
find, however, on a more attentive examination, that all the bones composing the 
skeleton in other vertebrated animals exist also in the Tortoise; and that the bony 
case which envelopes all the other parts is reg-lly formed by an extension of the 
spinous processes of the vertebrae and ribs on the one side, and of the usual pieces 
which compose the sternum on the other.” Vol. i. 1834, p. 464. The learned Pro- 
fessors of Comparative Anatomy in University College and King’s College, London, 
have in like manner adopted absolutely the determinations of Geoffroy St. Hilaire, 
although the former admits that-f-, “Looking at the singular exterior of these tortoises, 
shielded in a solid case like a molluscous animal in its shell, we should scarcely expect 
to find that this dense osseous covering enveloping the whole body consists of the same 
* Op. cit. p. 12. 
t Lancet, February 8, 1834. See also Prof. Grant’s ‘ Outlines of Comparative Anatomy,’ 8vo, 1835, p. 82. 
