1915.] | Allen, Review of the South American Sciuride. bio 
Tamiasciurus, as the name implies, is on the border line between the 
terrestrial and arboreal types, and differs morphologically more from the 
other North American arboreal squirrels than any other sciurid group except 
Microsciurus. Figures of the skull and maxillary teeth are given in com- 
parison with similar figures of Scturus vulgaris. 
Range.— The forested parts of the northern half of the North American 
continent. 
Genus Neosciurus. 
Plate III, Figs. 1-3; Plate VI, Figs. 12, 13. 
Neosciurus Trouessart, 1880 (subgenus of Sciurus). Type, by original 
designation and monotypy, Sciurus carolinensis Gmelin. 
Size medium; tail of medium length (about 46% of total length), broad 
and full; coloration not distinctive, gray above, white below. Mamme, 8. 
Premolars, ?; p* small, not reaching the crown level of p*; dentition not 
distinctive. Skull long and narrow, dorsal outline only slightly convex 
anterior to fronto-parietal suture; rostrum long and narrow, nasals narrow, 
moderately V-shaped on posterior border, about 33% of length of skull, 
93% of interorbital breadth; zygomatic breadth 55% of total length. 
Species: Neosciurus carolinensis, with numerous subspecies. 
Range, eastern half of United States. 
In cranial characters Neosciurys is similar to Otosciurus but it differs from 
it in external characters. 
Genus Otosciurus. 
Plate IV, Figs. 1-3; Plate VI, Fig. 16. 
Otosciurus ‘Nelson, 1899 (subgenus of Sciurus). Type, by original 
designation, Sciurus aberti Woodhouse. 
Size large, tail long and full (about 48% of total length). Lars large, 
heavily tufted in winter; upperparts gray with a reddish dorsal area; 
underparts white; an indistinct black lateral line. Mammae, 8. 
Premolars, ¢, p* strongly developed; dentition otherwise, and also cranial 
characters, nearly as in Neoscvurus. 
Range, southern Rocky Mountain region, from northern Colorado to 
Chihuahua and Durango, west to Arizona. 
Species: Otosciwrus aberti (with numerous subspecies), 0. durangi, and. 
O. kaibabensis. 
