1883. | The Extinct Rodentia of North America. 55 
The Haplodonta rufa is a curious burrowing rodent found in 
the Cascade mountains of Oregon, and is known as showtl or 
sewellel. It has no tail. 
The longest known species of this genus is the C. viciacensis, 
which is common in the Miocenes in several parts of Europe. 
In North America the C. nebrascensis Leidy, is stated by Hay- 
den and Leidy to be found in the White River formation. It is 
of about the same dimensions as the European species. So are the 
C. peninsulatus Cope, from the John Day River epoch of Oregon, 
and the C. pansus of the Loup Fork horizon of 
New Mexico and Nebraska (see Fig. 11). The 
smallest species is the C. gradatus Cope, a 
contemporary of the C. peninsulatus in Ore- 
gon. None of these species are nearly so large 
as the recent beaver. 
Eucastor Allen. 
Besides the preceding, there are some other 
forms of beavers in the late Tertiaries of North 
America and Europe. 
The Castor tortus was described by Leidy 
from the Loup Fork formation of Nebraska. 
He coined the subgeneric name Eucastor for 
it without corresponding definition. In his- 
monograph of the Castoride, J. A. Allen re- 
ferred this species! to a genus distinct from € 
Castor, and defined it, using for it Leidy’s aed seman ie ee 
name Eucastor, This genus appears to me to Shock va b, 30 4 pi 
be valid. The three genera of Castoridz will ge ee ee 
m Sherry Nat 
then be defined as follows: size. Origina 
Molars and premolars with one inner and two or three outer folds. ETE Castor, 
“ Inferior premolar and third superior molar elongate, with four enamel folds; the 
rest with only two” . . Diobroticus 
Superior premolar enlarged, with one inner fold; inferior dii a with two 
lakes... s o o Eucastor. 
1 Monographs of North American Rodentia, Coues and Allen, U. S. Geol. Surv. 
Terrs., 1877, Xt, p. 450. 
