~ 
1870. ] DR. J. E, GRAY ON THE DERMATEMYD. 713 
scutes, and the under borders of the fifth, sixth, and seventh mar- 
ginal scutes 5 these superadded scutes I propose to call ‘submar- 
ginal scutes. The Platysternon megacephalum, or large-headed 
Terrapin of the Chinese swamps, presents a corresponding but 
single supplementary ‘submarginal seute upon the under part ot 
each lateral production of the plastron.’’ ‘This statement about Pla- 
tysternon is entirely erroneous; for that genus, as well as Derma- 
temys and Pleurosternon, has three small “submarginal scutes ”’ 
between the abdominal and marginal plates (see Proceedings of the 
Zoological Society, 1831, p. 106, where the genus was originally de- 
scribed, and the ‘ Catalogue of Shield Reptiles,’ p- 49). The Pleu- 
rosterna are found in the freshwater limestone of Purbeck; and 
Professor Owen divides them into four species. I am still inclined 
to retain the genus, and I think that probably, when we have more 
materials, we shall find that the fossil genus will form a distinct 
group of the family. 
Mr. Agassiz, in his ‘Contributions to the Natural History of the 
United States,’ published in 1857, probably misled by Duméril’s 
figure, observes: —‘ Hmys berardi, Dum. et Bib., seems also to belong 
to this genus (Ptychemys), judging from the description and figure 
of the jaws uct an by A. Duméril, ‘ Archives du Museum,’ vol. vi. 
p. 251, t. 15” (vol. i. p. 434). 
The British Museum having received from Mr. Salvin a specimen 
of Dermatemys, which he obtained in Guatemala, I published in the 
* Proceedings of the Zoological Society,’ 1864, p. 125, a history of 
the genus and a description of the animal, which, unfortunately, was 
not in a very good state, as it had accidentally got dry through the 
evaporation of the spirit and had again been placed in spirit. 
In the ‘ Proceedings of the Academy of Natural Sciences’ for 
1868, p. 119, Mr. Cope describes a new species under the name of 
D. abnormis, from the Belize River, Yucatan, sent by Dr. Parsons, 
which differs in having the gular plates united and the vertebral 
plates broader than long. He observes that one species of Derma- 
temys, the D.mavei, is recognized by Dr. Gray as inhabiting Venezuela 
and Mexico. The same species, according to the same author, has 
been subsequently named Hmys berardii by Prot. Duméril; and he 
further remarks, “‘I have not had an opportunity of seeing South- 
American specimens; but the excellent figure and descriptions of 
Gray render it certain that the individuals from that country, on 
which the species are based, really belong to another species from 
those of Mexico. The collection of the Smithsonian Institution 
furnishes another species from Belize, which I have hitherto identified 
as the same; the species may be thus distinguished.” — In a table 
he gives the characters by which he proposes to discriminate three 
species, D. abnormis, D. berardii, and D. mavei. 
I do not know why he described his second species under the 
name of D, erardii ; for none of the characters which he gives to his 
species are to be found either mentioned in M. Duméril’s descriptions 
or shown in M. Duméril’s plate. I have no specimen possessing 
such characters as he gives to the species. 
