718 DR. J. E. GRAY ON THE GENUS BARTLETTIA. _[Noy. 1, 
the usual flat-backed Mud-Tortoises and the very convex Emyde of 
the Indian tanks, which have a series of marginal bones in the mar- 
gin of their cartilaginous dorsal shield. 
7. Notes on Bartlettia, a new Species of Freshwater Tor- 
toises belonging to the Family Peltocephalide. By 
Dr. J. E. Gray, F.R.S. &e. 
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 parti- 
cularly 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 dif- 
ferences in the form of the alveolar process, which has been con- 
firmed by the examination of the skulls or heads of a series of speci- 
mens 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. 
PELTOCEPHALID&. 
Peitocephalide, 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 de- 
pression on the side of the skull for the temporal muscle, is entirely 
formed, according to Prof. Owen, of an extension of the parietal bone. 
