OF THE BEAVER AND OF SOME SQUIBRELS. 1179 



is slightly emarginate above. In these three species the tragus is 

 small or absent. (Text-fig. 43, A, B.) In Ftonambidus tristriatus 

 the ear does not appear to differ in any essential points either 

 in structure or relative size from that of G. notatus\ but in 

 F. palmavvjm it is less hairy and relatively considerably larger 

 and has the posterior edge markedly emarginate above*. (Text- 

 fig. 42, D.) 



In the African Squirrels, Funiseiurus leucostigma aiid F. cepapi, 

 the eai'S are small as in Callosciurus, and do not appear to differ 

 from them, although the cavity is perha,ps more subdivided by 

 hollows and low ridges ; but in Heliosciurus pimctatus the anti- 

 tragus is better developed, being provided with a very definite 

 process ; the tragus is a curved, soft ridge, and the orifice of 

 the ear, normally concealed by the antitragus, is narrowed and 

 pointed above instead of being subcircular as in Funiseiurus. 

 (Text-fig. 43, C, D.) 



The ears of the Citellus, Cynomys, and Marmota are mostly 

 smaller than in the typical Squirrels ; but within the limits of 

 the genus Citellus the variation in size is considerable. In G. 

 {Otospermo2)hilus) heecheyi they are indeed relatively larger than 

 in Gallosciurus or Fuuisciiirus and project above the level of 

 the head ; but in other species, i. e. some of those referred to 

 the subgenus Ictidomys, they have been described by Allen as 

 " generally small, sometimes rudimentary." Nevertheless, even 

 in G. heecheyi they differ structurally from the ears of all the 

 typical Squirrels examined. The cavity of the ear, bou.nded 

 above by the supratragus, is to a considerable extent filled in 

 front by a thickened developm.ent of the inferior continuation 

 of the overturned anterior margin of the pinna ; and this 

 thickening is covered closely with longish hair covering the 

 cavity and closing it when the ear is folded. There is no trace 

 of tragus or antitragus, the lower rim of the cavity forming an 

 evenly curved line. For the rest, the area above the supratragus 

 is well developed and has a very distinctly emarginate posterior 

 border ; the tip is somewhat pointed, and the overfolding of the 

 edge of the anterior rim does not quite reach the summit. In front 

 the ear rises from the head at a point a little above the anterior 

 end of the supratragus, and behind the posterior border fuses 

 with the integument of the head just below the posterior end of 

 that ridge. (Text-fig. 44, D.) 



In Marmota inar^nota the ear is a little more reduced in size 

 than in Q. heecheyi^ and the area above the supratragus is wider 

 in proportion to its height ; the tip is pointed, but the posterior 

 border is less markedly emarginate. The points of origin of the 

 free portion in front and behind are approximately at the same 



* Judging from dried skins the ears of Tomeufes seera to be like those of 

 Callosciurus ; but in the remarkable Borneau genus RJieifJirosciurns these organs 

 differ from those of the other Oriental genera in their great length. In this 

 respect they surpass the eurs of S. vulgaris ; but details of their structure could not 

 be determined on the made-up skins in the Natural History Museum. 



