CARAPACE AND PLASTRON OF THE CHELONIAN REPTILES. 
155 
bones which compose the human skeleton:” and I must frankly avow that my expec- 
tation of such a discovery was so small as to beget neither surprise nor disappointment 
when the result of my researches into the development of the parts demonstrated on 
how superficial a view it had been entertained. 
Professor Rymer Jones, in his beautifully illustrated ‘ General Outline of the Animal 
Kingdom,’ adopting Cuvier’s determination of the ‘carapace’ and Geoffroy’s of the 
‘ plastron,’ observes, “ The margin of the dorsal ribs is further enlarged by a third 
set of flat bones, apparently representing the sternal ribs of the Crocodile.” 8vo, 1841, 
p. 553. In his article Reptilia, however, in Todd’s Cyclopsedia, Part 32, August, 
1848, — the latest opinion on the subject which has been published, — the Pi-ofessor 
affirms, “these marginal plates cannot be otherwise regarded than as the representa- 
tives of the sternal ribs of the Crocodiles and other Saurians.” P. 266. 
The German authors of standard works on comparative anatomy, with the excep- 
tion of Meckel=^, have manifested no such general acquiescence in the views of 
Geoffroy St. Hilaire, as that which characterises those of our countrymen above- 
cited. Carus, for example, originally regarded the immoveable ‘ costal plates ’ of the 
carapace as much-developed transverse processes, and the thorax of the Tortoise to 
be “only a more perfect development of the ribless and imperfect thorax of the 
Frog-f-;” — a view, however, in which his able English translator does not concur^; 
and which Carus himself abandons in the second edition of his work. He there 
states that the remarkable and anomalous skeleton of the trunk of the Chelonia may 
be explained by recognising how certain plates belonging primitively to the dermal 
skeleton are applied or adapted to the vertebrae, the ribs and the sternum the idea, 
however, is neither explained in detail nor supported by any fact of development, but 
is rather obscured by such fancies, as that the bodies of the vertebrae of the carapace 
are not formed, as usual, on the under side, but on the upper side of the vertebral 
column in the place of the spinous processes, which Carus affirms not to exist I], 
Dr. Peters^ adopts the view that the carapace includes dermal pieces besides the 
vertebrae and ribs ; and that the plastron consists of a subdivided sternum enlarged 
by combination with ossified parts of the integument. 
Professor Wagner has given us an opportunity of judging of the sense in which he 
* System der Vergleichenden Anatomie, Zweiter Theil, Erst. Abth. pp. 407, 408. 
t Introduction to Comparative Anatomy, by Gore, 8vo, 1827, p. 147. 
J See the note at the same page, where the Geoffroyian interpretation is given, as more correct. 
§ “ Die Bildung des Rumpfskelett’s nur dadurch erklarlich wird, das man einsehen lernt, wie durch Anbil- 
dung eigner, urspriinglich dem Hautskelet angehdriger Flatten an Riickgrath, Rippen und Brustbein, die auf 
den ersten blick so so nder bar abweichende Bildung des Riicken- und Bauchschildes zu Stande kommt.” Lehr- 
buch der Vergleich."^^^omie, 8vo. Bd. i. p. 164. 
II “ Am Riickenschilde das vbllige Verwachsen der Wirbel, deren kdrper hier nicht wie gewbhnlich an der 
untern, sondern an der obern Wirbelseite, statt naturlich ganz fehlenden, und durch die darauf gelegten Kno- 
chenplatten des Hautskelets ersetzlen Dornfortsatze ausgebildet sind.” Ib. p. 165. 
^ Observationes ad Anatomiam Cheloniorum, 1838. 
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