THE GIANT BEAVER i 
First Faunal Subzone the Heidelberg man (Homo hetdel- 
bergensis) was contemporary with Trogonthervum, and of 
course with Castor fiber, the European beaver, which 
existed at the same time. Trogontherium survived until 
the lower part of the Middle Pleistocene. 
Castor is widespread in North American Pleistocene, 
but is lacking from the Pliocene and earlier formations of 
that continent. It occurs in deposits which are very early 
Pleistocene, as at Fossil Lake, near Christmas Lake, Ore- 
gon; on the Niobrara River, 15 miles from Hay Springs, 
Nebraska; and the Port Kennedy Cave, Pennsylvania. 
Dipoides was a rodent about the size of a marmot whose 
remains have been found in western North America from 
the Upper Miocene up to the Pliocene. Matthews and 
Cook have remarked that Dipoides shows a marked ap- 
proach to Castoroides. It may bean ancestor of that genus. 
THE GIANT BEAVER, CASTOROIDES 
The giant beavers, belonging to the genus Castoroides, 
though closely related to the beaver, are placed in a dif- 
ferent family, Castoroidide. 'They were exclusively North 
American animals. 
The geological range of this genus is from deposits which 
belong very near the beginning of the Pleistocene, upward 
all through that epoch, while numerous specimens have 
been found overlying the last or Wisconsin Drift, showing 
that the animal existed long after the glacial ice had dis- 
appeared. In the lower deposits it is found associated 
with horses and camels, and also with remains of the true 
beavers of the genus Castor. Specimens have been found 
in many parts of the country from central New York to 
the Great Plains, and also at Fossil Lake, near Christmas 
Lake, Oregon; and from Florida to Minnesota. A. G. 
