A new Niobrara toxochelys / by G.R. Wieland.

  • Wieland, G. R. (George Reber), 1865-1953.
Date:
[1905]
Catalogue details

Licence: In copyright

Credit: A new Niobrara toxochelys / by G.R. Wieland. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    ogy of the osteodermal mosaic of Dermoehelys (6, 7). The present is, however, the first time that the entire series of ossicles and their relation to the successive neurals has been determined. As may be judged from reference to the several ligures, the system of ossicles may really he a much changed and disappearing one. The first neural hears a small hut very distinct completely fused boss near its middle, and then forms the beginning of the dorsal carina. The third neural which is rather short, and the fourth which is abnormally long, support a large epi-neural spine. This occupies all the median poste- rior three-fourths of the length of the third and the anterior fourth of the length of the fourth neurals, and is doubtless the second member of the original epi-neural series. The second free epi-neural [or third of the original series] is the largest, and is equally borne by the fifth and sixth neurals. The third free epi-neural [or fourth of the hypothetical primitive series] rests over the ninth member of the neuralia, so as to project slightly forward onto the eighth and well backward over all the anterior half of the post-neural tenth. This latter epi- neural is the smallest of the three free epi-neurals. 4 & Figure 4.—Toxochelys Bauri type, x1/,. a, Vertical transverse section through the second neural showing the average elevation and outline of the median neural carina. b, Vertical transverse section through anterior end of the 6th neural, and the epi-neural spine (s) borne on this and the 5tli neurals. Whether a fifth member of the epi-neural series was boijne by the postero-pygal, which would afford the symmetrical posi- tion, is of course conjectural in the absence of this latter member of the median series.