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Show 718 DR. J. E. GRAY ON THE GENUS BARTLETTIA. [Nov. 1, the usual flat-backed Mud-Tortoises and the very convex Emydce of the Indian tanks, which have a series of marginal bones in the margin of their cartilaginous dorsal shield. 7. Notes on Bartlettia, a new Species of Freshwater Tortoises belonging to the Family Peltocephalidae. By Dr. J. E. G R A Y , F.R.S. &c. It has been well observed that after the greatest care some new fact in the structure of an animal that has been often observed will occur. I have been for several years collecting together the species of Tortoises, and more especially studying the osteology, and particularly the skulls of the Testudinata ; I have published several papers on them, and have collected these papers together, with many additional observations and descriptions, as a ' Supplement to the Catalogue of Shield Reptiles in the British Museum,' which is printed and ready for distribution ; and yet, before it has actually been published, an accidental circumstance has revealed to me that a series of specimens that I believed were all of one species, coming from nearly the same locality, consists of two most distinct species, belonging to two most distinct genera, marked by very great differences in the form of the alveolar process, which has been confirmed by the examination of the skulls or heads of a series of specimens of each species of different ages. Mr. Edward Bartlett, during his excursion to Brazil for the purpose of collecting objects of natural history, sent to the Museum a series of specimens of a freshwater Tortoise which he obtained in the freshwater lakes in the region of the upper Amazons. They were considered to be half-grown examples of Podocnemis expansa, which they greatly resemble in all external characters; but on Mr. Edward Gerrard, junior, preparing a skeleton of one of them for the collection, it was discovered that it possessed a very different alveolar surface of the upper jaw ; and on examining the jaws of the other specimens, they were all found to have the same peculiar character; therefore I have described and figured these jaws; and to point out, in the shortest manner, the differences between it and the other genera of the family, I have formed a tabular distribution of them. PELTOCEPHALIDAE. Peltocephalidce, Gray, Suppl. Cat. Sh. Rept. p. 82. In the skulls of all the genera in this family the vomer is not ossified, and the internal nostrils of the skull are not divided by a septum, but leave a large open aperture in the front of the palate. The bony vaulted arch that covers more or less completely the depression on the side of the skull for the temporal muscle, is entirely formed, according to Prof. Owen, of an extension of the parietal bone. |