Vol. IV] GRINNELL AND SWARTH—SAN JACINTO GOPHERS ^^57 



As the structural peculiarities of jacinteus point to close 

 affinities with other boreal species from distant mountains, 

 rather than with the geographically nearer low-zone species of 

 the same mountain mass, there is, of course, no need for in- 

 voking a theory of isolation from nigricans to account for the 

 occurrence of the former on San Jacinto Peak. It is, how- 

 ever, of decided interest to note the probable existence of asso- 

 ciational barriers to the dispersal of an animal with the habits 

 of the gopher, along the exact line where division between 

 jacinteus and nigricans appears to be. While these barriers 

 may have had nothing to do with the origin of either species, 

 they may well be the sole prevention of the wider dispersal of 

 either one of them, which, if it had been freely possible, might 

 have resulted in competitive displacement of the other. 



The summer of 1914 had been an unusually dry one in the 

 San Jacinto Mountains, where this season of the year is gen- 

 erally accompanied by frequent thunder showers ; and in the 

 lower parts of the range the dryness had the effect of entirely 

 stopping the gophers from any active digging. In Strawberry 

 Valley, during two weeks, no freshly thrown-out earth was 

 seen, though Thomomys nigricans is an abundant inhabitant 

 of the valley, and old mounds could be observed everywhere. 

 It was evident, however, that the cessation of digging activities 

 by the animals was by no means an indication that they were in 

 a dormant condition similar to hibernation. A house cat be- 

 longing to an acquaintance in the camp caught gophers fre- 

 quently, sometimes two in a night. 



Trapping here was not promising, however, for there was 

 no way of telling which entrances were in use ; so it was a re- 

 lief to find that conditions were somewhat different in the 

 higher valleys where jacinteus occurs. The several large mead- 

 ows occupying the centers of Tahquitz and Round valleys are 

 so saturated with water that even in a dry summer parts of 

 them remain boggy. About these wet meadows the gophers 

 were most abundant. No trapping was done in Tahquitz 

 Valley during the visit of September, 1914, and but a cursory 

 investigation of conditions was made; but several fresh 

 mounds were noted near the edges of the meadow and on the 

 adjacent dry ridges. 



