OF THE BEAVER AND OF SOME SQUrRRELS. 



1175 



open into the mouth approximately on a level with the anterior 

 end of the molar teeth. In Tamias they are of large size, and, 

 when imstretched, reach back as far as the ear. In Gynomys 

 they are much smaller and do not reach beyond the eye. Judging 

 from the descriptions of the pouch of Citellus as " large," I 

 presume it resembles that of Tamias and Eutainias. Marinota 

 is usually described as being without cheek pouches, and I failed 

 to find a trace of them in the ty^pical European species M. 

 miarmota. Nevertheless, in his diagnosis of the genus. Miller 



Text-figure 40. 



A. Muzzle and I'liinarium of Castor fiber. 



B. Rhiiiarium of the same from the side. 



C. Ear of Castor fiber, with position of orifice dotted in. 



says " cheek pouches rudimentary or absent." Elliot * describes 

 them as small in the American species, assigned to Marinota. 

 and Cory f cites their presence as a character of the subfamily 

 Marmotinm. (Text-fig. 41, 0, D.) Fresh information is clearly 

 wanted on this point. 



In its palatal and lingual lobes the mouth of Castor resembles 

 that of the Sciuridas, but it differs in having a lai'ge pad on each 

 side of the cheek, lying farther within the mouth than the 

 noi-mal lobes. Each of these pads is provided with stiff, short 



* Field Columbian Museum, Zool. ii. p. 104, 1901. 

 ■ t ' The Mammals of Illinois and Wisconsin,' p, 137, 1913. 



78* 



