Vol. IV] GRINNELL AND SWARTH—SAN JACINTO GOPHERS 2^55 



much less reddish-brown tone of coloration, in more or less 

 white marking about the face, in heavier dentition, in larger 

 and especially more elongated auditory bullae, in wider inter- 

 orbital constriction, in less widely spreading zygomatic arches, 

 and in more nearly straight dorsal outline of skull in lateral 

 profile. 



Taking all characters into consideration, there appear to be 

 more in common between jacinteus and alpinus than between 

 jacinteus and altivallis. Out of the entire series of jacinteus, 

 both adults and young, eleven have much white on chin and 

 lining of cheek-pouches, as in alpinus; the rest all show white 

 in lining of cheek-pouches, at least. Altivallis has a blackish 

 brown face, rarely showing white, even within the cheek- 

 pouches. 



Relationships and Ecology. — The habitats of the several 

 species of Thomomys occurring in the San Jacinto Mountains 

 seem to be constituted mainly by the several valleys compris- 

 ing areas of varying size throughout the range. Thomas (or 

 Hemet), Strawberry, Tahquitz, and Round valleys are the 

 more important of the stretches of comparatively open and 

 level country of the higher parts of the mountains ; and while 

 gophers also occur in limited numbers along some of the 

 streams connecting these sections, as well as on many of the 

 dry and rather open pine-covered ridges, still the meadow- 

 lands in each of these valleys may be considered as the cen- 

 ters of abundance and radial dispersal of the gophers of these 

 mountains. The densely brush-covered slopes surrounding the 

 lower valleys offer poor inducements to the species, and the 

 animals are seldom found in such places. 



The three higher valleys of San Jacinto Peak, Strawberry 

 Valley at 6000 feet, Tahquitz Valley at 8000 feet, and Round 

 Valley at 9000 feet, form a series of terraces on the sides of 

 the mountain. In these mountain valleys the soil is deep and 

 rich, in many places supporting a dense growth of grasses, and 

 sometimes so saturated with water as to form acres of wet bog, 

 altogether making most favorable surroundings for gophers. 

 In striking contrast, the valleys' edges are sharply defined by 

 steep, rocky slopes, these in the higher portions of the range 

 frequently forming series of bare cliffs, in the lower parts steep, 

 gravelly hillsides, densely covered with chaparral. 



