1180 



MR, E. I. POCOCK ON THE EXTERNAL CHARACTERS 



levels as in C. heecheyi ; the cavity is similarly blocked in front 

 by the hairy thickening of the injutting portion of the inferior 

 continuation of the overfoldecl portion of the anterior rim, and 

 there is no trace of tragus, antitragus, or interti-agal notch. 

 (Text-fig. 44, E.) 



In Cynomys the eai- is very much smaller than in Marmota 

 owing to the reduction in size of the area above the supratragus. 

 The summit is rounded, and has its edge overfolded in continua- 

 tion of the overfolding of the anterior edge. The hairy thick- 

 ening projecting backwards into the cavity of the ear above the 

 orifice is well developed, there is no tragus or intertragal notch, 

 and at most a trace of antitragal thickening. (Text-fig. 44, F.) 



In the Ground Squirrels of the genus Xerus and its allies, 

 which are as terrestrial in their habits as the Sousliks and 



Text-fig;ure 43. 



A 



at. 



p 



A. Ear of Callosciiirus prevosti. 



B. „ „ Tomeutes vittatus. 



C. ,, „ Funisciurus cepapi. 



D. Ear of Seliosciurus punctatus. 



E. „ „ Atlmitoxerus getuhis. 



F. „ „ Greosciurus capensis. 



at., autitragal thickening. 



Marmots, the ears are greatly reduced in size, in some cases, 

 indeed, e. g. in Geosciurus capensis., equalling apparently in that 

 respect those of some of the small-eared species of Citellus. But 

 they are modified for terrestrial life on quite a different plan 

 from that exhibited by the Sousliks and Marmots. 



In JEuxei-tis erythropits, for instance, a comparatively large- 

 eared form, in which the summit of the ear reaches about as 

 high as the level of the head, the antero-superior and posterior 

 margins meet approximately at a right angle. The anterior edge 

 is overfolded, and is continued beneath the supratragus, where 

 it bends backwards and downwards, ceasing just above the 

 tragus, or sometimes running thence backwards and upwards as 



