﻿Dec, 1895.] 



^^OREX RICHARDSONI. 



49 



facej this area broadest over kirabar region and shoulders, narrowest 

 just back of shoulders; sides yellowish hair brown in striking contrast, 

 this color clear and pure from flauks to sides of head but across the 

 face mixing with the walnut brown of the back; belly pale hair brown; 

 an indistiuct line of demarcation between colors of belly and sides; 

 ventral surface of tail and dorsum of manus and pes concolor with 

 sides; tail seal brown dorsally and at tip, though not sharply bicolor. 

 In summer: Back dull seal brown, darker over rump and lumbar 

 region; sides light sepia, darker on shoulders and flanks; belly uniform 

 pale broccoli brown. Feet and tail as in winter. There is m summer 

 much more color variation than in winter. A few individuals are then 

 as dark as in winter, but the majority are paler. The palest specimen 

 that I have seen is dark hair brown on the back, pale sepia on the sides, 

 and broccoli brown on the belly. The line of demarcation between the 

 colors of the back and sides is always well marked, though the color of 

 the latter often fades insensibly into that of the belly. 



Slcull — Tlie skull of Sorex richardsom (PL YI, fig. 4) is indistinguish- 

 able from that of Sorex araneus (PI. YI, fig. 3). The brain case is well 

 rounded and moderately high, less so than in Sorex palustris and S. 

 alhiharhis. The rostrum is slender (narrower than in S. fumeus), and 

 as compared with the species of the minutiis group rather deep (see 

 table, page 43). The anterior opening of the infraorbital canal is 

 subcircular, the outline distinct on the lower and posterior borders, the 

 posterior border over a point a little in advance of the middle of the 

 first molar. The lachrymal foramen opens exactly over the middle of 

 the first molar. 



Teeth. — In general the teeth of Sorex richardsoni resemble those of 

 S. araneus very closely, differing chiefly in their slightly larger size 

 and in a few details in the proportions of the unicuspids. The lat- 

 ter (PI. Y, fig. 4), like the skull, are strongly and heavily built. The 

 second and third incisors are subequal, the second usually the larger. 

 The canine and the fourth incisor are subequal, the latter always the 

 larger of the two and either intermediate in size between the canine 

 and the third incisor or more nearly the size of the canine. The pre- 

 molar is small, but distinctly visible from the outer side. The teeth are 

 strongly colored at the points, the colored area on the front incisors of 

 both jaws being continuous, and on the unicuspids occupying a little 

 less than one-third of the outer face of the unworn teeth. 



While the teeth of Sorex richardsoni resemble those of both Sorex 

 fumens and Sorex araneus^ they are more like the latter. From the 

 teeth of the former they differ m larger size, more extensive pigmen- 

 tation, and greater relative size of the canine and fourth incisor. From 

 the teeth of S. araneus those of S. richardsoni may be distinguished by 

 the proportionally smaller premolar and larger canine. From both 

 araneus and fumeus^ richardsoni differs in the less extensive excava- 

 tion of the posterior borders of the upper molariform teeth. 

 4110— No. 10 4 



