EXPLANATION OF PLATE II. 



Ondatra zibelhica Linnaeus. 



Dorsal, ventral, and lateral views of skull and mandible of new-born 

 animal (enlarged). The eondylo-basal length of this skull is 27 mm. 

 The Plate should be compared with Figs. 44-^6, which represent an 

 adult skull of Otidatra zibethica, and with Figs. 1-7, which represent 

 successive stages of growth m the skull of Arvicola amphibius. 



The unworn Wj shown in Fig. 58 and described at p. 115 belongs to the 

 specimen represented in this Plate. 



