45Q 



R0DEXT1A 



continent. According to Mr. 0. Thomas, 1 the latter " little animal 

 is most nearly allied to the West-African A. beecrofti, but differs 

 from that species in its duller and less yellow upper side, in the 

 entire absence of rufous on its neck and belly, and, as from all the 

 other described species, in its diminutive size." 



Fig. 10S. 



-Lateral view of skull of American Marmot 

 (Arctomys monax). 



Fa mily SciURiD.E. 



Arboreal or terrestrial forms, with cylindrical hairy tails, with- 

 out scales, and with 

 twelve or thirteen 

 pairs of ribs. Skull 

 (Figs. 198, 199) with 

 distinct postorbital 

 processes; infra- 

 orbital opening 

 small; palate broad; 

 p f ; first upper pre- 

 molar very small or 

 deciduous ; molars 

 rooted, tubercular. 



Subfamily Seiur- 

 inse. — Incisors com- 

 pressed ; form slen- 

 der ; tail long and 



hairy. Cosmopolitan (excluding Australian region). 



This subfamily includes the true Squirrels, of which seven 



existing genera are usually recognised. 



Sciurus. 2 — Tail long and bushy ; ears generally well developed, 



pointed, often tufted ; 



feet adapted for climb- 

 ing, the anterior hav- 

 ing four digits and 



a rudimentary pollex, 



and the posterior with 



five digits, all of which 



have long, curved, and 



sharp claws. Mammae, 



from four to six. Skull 



(Fig. 199) lightly built, 



with long postorbital 



processes. Penultimate 



upper premolar, when 



present, minute. 



Fig. 199.- 



- Palatal Aspect of cranium of Squirrel (Sciurus 

 bicolor). Natural size. 



1 Proc. Zool. Hoc. 1882, p. S. 



Linn. Syst. Nat. 12th ed. vol. i. \>. 86 (1766). 



