332 The American Geologist. •^"°^' ^^^^ 
plastron. The expedition of 1903 obtained this and a por- 
tion of a skull. Furthermore, a good specimen of the 
species has been described by the writer from the Yale 
University Museum, which furnished a good plastron and 
most of the skull. The genus is to be assigned to the 
Dermatemydidae, now represented in Central America by 
three genera. 
The family Anostciridae is represented in the Bridger 
by the single genus Anosteira. It is not well known, only 
the shell having so far been discovered. The two species 
A. ornata Leidy and A. radulina Cope were of rather small 
size. They possessed beautifully sculptured shells. It is 
usually supposed that they were closely related to our 
modern snapping turtles, but a discovery of the rest of the 
skeleton might greatly piodify this opinion. A large and 
imperfectly preserved species belonging to the Upper 
Eocene of England has been referred to this genus. 
Of the Emydidae, the pond and river turtles, there are 
known eight Bridger species, all of which have been de- 
scribed by Leidy and Cope. In the Mississippi valle)'- 
north of Tennessee, we find only about a dozen living 
species of Emydidae. The Bridger species have hitherto 
been placed in the genus Emys, but they certainly do not 
belong to this. They are more 'closely related to species of 
the genera Chrysemys and Clemmys. Notwithstanding 
the great number of species and individuals of this family 
which occur in the Bridger beds, only a portion of one skull 
has yet been found, and this is not associated with the re- 
mainder of the skeleton. This skull shows only a feeble 
development of the ridge on the masticatory surface of the 
upper jaw. It is not improbable that, when skulls shall 
have been found, these Bridger species of Emydidae will 
have to be placed in some new genus or genera. There can 
be no doubt that the habits of these Emydidae were essen- 
tially such as our modern river and pond turtles display. 
They haunted the borders of the streams, they captured 
living prey, cind they betook themselves to the bottoms of 
the streams for protection from their enemies. Usually the 
shells are thick, a condition indicating probably in some 
cases a habitation in swift streams ; in other cases possibly 
