CLASSIFICATION OF THE SCIURIDiE. 237 



Subfamily Sciukin^. 



Grlans penis apically expanded, compressed and upturned, 

 enveloped behind the upturned tip in soft swollen tissue. 

 Baculum large, with compressed terminal blade hollowed on the 

 right side, which carries inferiorly a short downwardly directed 

 process. 



Ears relatively long, more tubular at the base, with large 

 angular antitagral flap. 



Feet with fourth digit the longest ; the plantar, carpal, and 

 metatarsal pads normal and relatively simple. 



Genera: Sciurus, with subgenus Tenes^ ior i^ersicus; all the 

 American subgenera or genera, Neosciurus, Farasciurus, 

 Echinosciiirus, etc., except Tamiaschorus ; '^. Bheithro- 

 sciu7't(,s. 



DistriMUion. Holarctic and Neotropical Regions and ? Borneo 

 ( Rheithrosciurus), 



I feel compelled to include liheithroscmms provisionally in this 

 group, pending confirmation or refutation of Thomas's statement 

 that the baculum is like that of Sciui'us. In other external 

 characters supplied by the ears and feet it is certainly unlike 

 other Oriental species and comes nearer to Scucrus. On the 

 evidence at present available I should judge it to be a highly 

 specialised member of the Sciurinse as above defined. 



Subfamily Tamiasciurin^, 



Distinguishable from the Sciurinag, Avhich it resembles in 

 cranial and other external characters, by the structure of the 

 penis, which is relatively long and slender and tolerably evenly 

 attenuated from base to apex, and flexible throughout owing to 

 the suppression of the baculum. 



Genus Tamiaschirus. 

 Distribution. Nearctic Subregion, 



The general resemblance between Tamiascmrus and the typical 

 Sciurinse suggests that it is a specialised ofi'shoot of that group. 

 It is a very remarkable fact that the extreme differentiation of 

 the penis does not appear to be correlated with other variations 

 from the Scivxrine type. 



In the structure of the penis Tam.iasciurus shows to a certain 

 extent a convergent* resemblance to the African genus Helio- 

 sciurus (see below, p. 238). 



Subfamily Funambulin^. 



A highly diversified group of genera, with the glans penis 

 exceedingly variable in size and sti'ucture and the baculum either 



* Thomas, Anu. & Mag. N. Hist. (8) iii. p. 468 (1909). 



