Zoology. 137 
condition in Platemys Bowerbankii, mg rem Phan of 
Owen presents the intermarginal scuta of Plewrosternum, an 
because of the general resemblance in speci anaee between 
the latter and the Pl. concinnuwm. To us, however, the genus 
Pleurosternum appears to be Cryptodire oe ’Pleurodire, as it lacks 
the integular scutum of the latter suborder, and to represent a 
peculiar family of that group pogrinaieaae” by the eae of 
ten instead of eight sternal bones. Platemys Bullockii, P. Bow 
bankii and Emys levis Ow. and Bell appear on the other ric 
to be useotes, and to be si to pee families of that sub- 
order. e Pl. Bullockii, on account of its five pairs of sternal 
bones, to the Sternotherid, and on acco nt of its intermarginal 
seuta, to anew genus s which I have called Digerrhum. The last 
wo, in their rudimental fifth pair of sternals resemble many 
Homedics, and cannot be distinguished from = genus Podoc- 
nemis now living in the Amazon. e tL. catus Laity is 
near to Podocnemis also, but represents a aetiet¢ genus, character- 
istic of the ——* which I call Taphrosphys ; there are six 
species in North America. After these deductions the only Pla- 
temydes that nina are P. Mantellit and P. Dixonii of Owen. 
mo man 
those of ey latter, while th ose of the limbs, the — fee in 
this case, are those of the former. Two of the North American 
genera add one or two costal bones, a character of i aa a pa and 
one not hitherto met with in the order ; these may be regarded as 
the type of a peculiar family with the name of the Propleuride, 
including the genera Osteopygis and Propleura. The family with 
eight costals includes Chelonides Maack, which seems to be near 
Chelonemys Jourd., as he has placed it, —with Platychelys, Hydro- 
pelta, Idiocheiys and ane other European forms which, with Cata- 
pleura and m North America, are nearer 
and I cannot at present find characters which distinguish them as 
a famil existin In Stylemys Maack, the second 
new introduced into the present work, the sternum is wit 
ygis. Un 
as an Himydoid, as placed by Dr. Maack. Two species are de- 
scribed, S. Lindenensis and 8. Hannoveranus. The use of the name 
Stylemys i is a faue pas, since it must probably be used for a genus 
of Emydide described by Leidy from age Miocene and Pliocene of 
Nebraska and Dakota. True, it was originally established on 
untenable characters, and reunited ts en proposer with Zestudo, 
But I have been able to point out (Trans. Amer. Phil. Soc., ee 
123) that the pan so originally named are really Emydi 
