944 RODENTIA 



actually as well as relatively larger than in Sclurus vulgaris, and 

 less well defined posteriorly owing to aljsence of distinct anterior 

 concavity and median projection on upper border of zygoma, 

 its orifice directed more upward. Zygoma no more abruptly 

 spreading than in Sciurus vulgaris, but the arches appearing 

 wider by contrast with the narrower interorbital region, and also 

 on account of the much more abrupt angle at which the anterior 

 surface of zygomatic root meets outer surface of rostrum ; median 

 portion of arch splayed so strongly outward as to be almost 

 horizontal ; jugal projecting posteriorly behind zygomatic process 

 of squamosal, its u})per border without angular median projection, 

 its anterior extremity running upward nearly to lachrymal ; 

 anteorbital foramen small, nearly circular, scarcely in front 

 of level of anterior premolar, hidden in lateral view by the 

 conspicuously projecting process formed by lower portion of its 

 outer border. Rostrum relatively somewhat shorter than in 

 Sciurus vulgaris, its base so narrow that its sides are nearly 

 parallel, the least depth behind incisors somewhat greater than 

 width in same region ; nasals rather short, abruptly narrowed 

 posteriorly, their slightly emarginate hinder border lying at level 

 of posterior base of zygomatic root, the moderately expanded 

 nasal branches of premaxillaries scarcely extending behind them. 

 Palate relatively about as wide as in Sciurus vulgaris ; incisive 

 foramina large but lying almost entirely within premaxillaries, 

 the posterior border of which is therefore relatively much further 

 back (under middle of zygomatic root) than in Sciurus vulgaris, 

 the greatest length of foramina exceeding least width of rostrum 

 and equal to somewhat more than half dia.stema ; region behind 

 notch back of m'' conspicuously thickened ; mesopterygoid space 

 about as long as in Sciurus vulgaris, but conspicuously wider 

 anteriorly than posteriorly. Mandible with anterior portion of 

 ramus less deepened and more curved than in Sciurus vulgaris ; 

 posterior region so deep and short that greatest depth (exclusive 

 of coronoid) is nearly equal to distance from condyle to front of 

 wii, while in S. vulgaris the same depth barely equals distance 

 from condyle to back of m.^ ; coronoid process low and short, 

 strongly curved backward ; angular process large, its broad apex 

 curving abruptly outward, its lower border greatly developed 

 and forming almost a separate lobe bent strongly inward. 



rct'/^.—Incisors less compressed than those of Sciurus vulgaris, 

 the roots forming no evident protuberances, the anterior surface 

 smooth, deep orange in colour. Anterior upper premolar terete, 

 its crown simple, about one-fourth or one-fifth that of succeeding 

 tooth in area. Upper molariform teeth resembling those of 

 Sciurus vulgaris in their relative sizes and general structure ; 

 anterior border of crown more elevated, its outer extremity 

 appearing as a distinct cusp nearly as high as the two main 

 cusps when tooth is viewed from the side; main transverse 

 ridges relatively higher and narrower, the second, except in m^, 



