EXPLANATION OF PLATE 26 
Dorsal view of crania of woodchuck, aplodontia, and beaver; all xX 0.50. 
Fig. 4, Marmota flaviventris sierrae, no. 15165, Mus. Vert. Zool.; fig. 5, Aplodontia 
rufa californica, no. 18663, Mus. Vert. Zool.; fig. 6, Castor subauratus subauratus, 
no. 12654, Mus. Vert. Zool. 
Note in Aplodontia and Castor the absence of postorbital processes on the 
frontal; also the comparative width of the cranium posteriorly in Aplodontia, 
as compared with Marmota and Castor. 
[ 498 ] 
