U. 8 GEOLOGICAL SURVEY OF THE TERRITORIES. MURID&, PLATE Iv. 
Figs. 42-45, Arvicola riparius (1949), Vigs. 46-49, A. ripariuas (4858). ? 
Figs. 50-53, A, townsendi (6892). Figs. 54-57, A. xanthognaihus (12178), 
