File:Image from page 604 of "On the anatomy of vertebrates (electronic resource)" (1866) (14752456361).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

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Text Appearing Before Image: he trunk, wherenot ossified, in Triojiycidce, has the dermal tissue of cartilaginoushardness. In the Turtles, or marine Chelonia, besides the eight connateneural plates, fig. 52, 51-58 (p. 61), dermal bones are developedin advance of and behind them, and are commonly unattachedto the subjacent vertebrae. The anterior one, ib. ch, is the( nuchal plate: the posterior one, ib. py, is the pygal plate ;the costal plates, ph-ph, articulate suturally with the neuralplates, but do not extend to the end of the ribs; the marginalplates, mi-mvi, are articulated with each other and with thenuchal and pygal plates suturally, and eight on each side receivethe ends of the eight ribs supporting the costal plates. Two TEGUMENTS OF REPTILES. 559 pairs of dermal bones are developed from the hyo- and hypo-sternals, fig. 53, lis and ps: but these do not articulate with themarginal series. In Freshwater and Land Tortoises the dermalossifications spread further, uniting all the parts of the plastron 371 372

Text Appearing After Image: Outer surface, plastron, young Tortoise. Inner surface, plastron, young Tortoise. into one more or less flat floor, and all the parts of the carapaceinto one more or less convex roof, fig. 51; side-walls being like-wise now formed by the union of the hyo- and hypo-sternalswith the coextensive marginal plates. In all Chelonia, save theTrionycidce and Sphargis, the epiderm of the trunk is condensedinto large horny scales, usually contiguous, more rarely imbricate,and then only on the carapace. They may be keeled, or rugous,or scabrous, but are commonly smooth and polished, or markedonly by concentric lines of growth. Their growing marginsindent the dermal bones supporting them, forming the triradiategrooves, e. g. upon the beginnings of the costal plates in theyoung Tortoise, fig. 370, ph, and those marked si-s5 on theneural and costal plates in the Turtle, fig. 52. The large epi-dermal plates of the carapace and plastron are termed ( shieldsand e tortoise-shell: most of them have speci

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