Volume 1

Monograph on the fossil reptilia of the London clay / by Professor Owen and Professor Bell.

  • Owen, Richard, 1804-1892.
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: Monograph on the fossil reptilia of the London clay / by Professor Owen and Professor Bell. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    developments of the vertebral ribs (pleurapophyses),* and the marginal pieces as the honiologues of the sternal ribs (haemapophyses).t I mnst refer the reader to my Memoir, communicated to the Royal Society, for the facts and arguments wliich have led me to regard these pieces, as dermal ossifications, homologous with those that support the nuchal and dorsal epidermal scutes in the crocodile. Most of the bony pieces of the carapace are, however, directly continuous, and connate,]: with the obvious elements of the vertebrae, which have been supposed exclusively to form them by their unusual development; the median pieces have accordingly been called “ vertebral plates,” and the medio-lateral pieces “ costal plates.” I retain the latter name, although with the understanding and conviction that they are essentially or homologically distinct parts from the vertebral ribs or pleurapophyses with which they are connate and more or less blended. But, with regard to the term “ vertebral” plate, since the ribs {costa) are as essentially elements of the vertebra as the spinous processes themselves, I have been in the habit, in my Lectures, of indicating the median series by the term “ neural plates,” which term has the further advantage of removing any ambiguity from the descriptions that might arise from their being mistaken for the superincumbent epidermal shields, which are likewise called “vertebral plates” m some English works.§ The term “marginal” is retained for the osseous ])latcs forming the periphery of the carapace; l)ut the median and symmetrical ones, which seem also to begin and end the “ neural” series, are specified, the one by the term “ nuchal plate,” the other by that of “ pygal plate.” The “ neural plates” are numbered as in the classical Monograph of Bojanus.|| In the subjoined woodcut of the carapace of the loggerhead turtle (fig. \),ch is the nuchal plate; -si to -si i the neural plates ; />/i to p>h the eostal plates; and m\ to ni\2 the marginal plates. The carapace is im])ressed by the superimposed epidermal scutes or shields, which consist of a median series, called “ vertebral scutes' v\ to V5 ; Ibid. p. 211. Rathke lias recently supported this determination by arguments drawn from the mode of development of the carapace. See ‘ Anuales des Sciences Naturelles,’ Mars, 1846 ; and ‘Ueber die Entwickelung der Schildkrdten,’ 4to, 1848, where he says, p. 105 :—“ Ausser den Rippen und den horizontal liegenden Tafeln, zu welcben sich die Dornfortsiitze des zweiten und der sechs folgenden Riickenwirbel ausbilden, dienen bei den erwachsenen Schildkidten zur Zusammensetzung des Riickenschildes noch eine Oder mehrere Knochenplatten,” viz. the “ marginal plates.” I have shown how Rathke was deceived by over-estimating the character of connation, in my ‘ Observations on the Development of the Carapace and Plastron of the Chelonians,’ which conduct to a different conclusion to that at which Cuvier and Rathke have arrived. (Philosoph. Transactions, 1849.) t Geofi'roy, Annales du Museum, tom. xiv (1809), p. 7. J This term is used in the definite sense explained in my work on the ‘Archetype of the Vertebrate Skeleton’ (8vo, V. Voorst, p. 49), as signifying those essentially different parts which are not physically distinct at any stage of development; and in contradistinction to the term “ confluent,” which applies to those united parts which were originally distinct. § See Griffiths’s translation of Cuvier, vol. ix. Synopsis of Reptilia, p. 6—“fifth vertebral plates prominent.”