230 University of California PuMioa-iions in Zoology [Vol. 21 



dorsal areas and of the sides, except that in the case of eureka the 

 tone is somewhat brighter in mass effect, and the dorsal areas of the 

 least worn specimens are often paler. Skins of the two may be dis- 

 tinguished by a glance at the underparts, which in trinotatus are 

 mainly pure white, with the central area and a small portion of the 

 lower throat tinged with a lighter shade of the lateral color, while the 

 underparts of eureka are evenly and uniformly so tinged. In the 

 single spring specimen that is at hand of eureka, the dorsal area is 

 fairly well defibned, but is a trifle paler anteriorly, with a grayish cast. 

 The inguinal region and the underparts immediately contiguous to 

 the forefeet are white, while the hairs of the remainder of the under- 

 parts are strongly tipped with ochraceous buff, and the lateral tone 

 is a more intense shade of the same color, very much as in orarius. 



Skull. — This form and orarius have especially tapering rostra and 

 large bullae. Eureka differs from trinotatus as remarked above. For 

 comparison with orarius, see under that species. 



Measurements. — Average, in the flesh, of 15 apparently adult 

 specimens from Humboldt County, California : length, 228.3 mm. ; 

 tail, 144; foot, 33.1. Average of 11 Z. t. trinotatus from northern 

 Washington: length, 230.5; tail, 145.4; foot, 31.1. 



Remarks.- — The California coast forms of Zapus are evidently con- 

 fined to the narrow, humid strip between the dense forests of the 

 Coast Range and the sea, though they may extend up the more open 

 river valleys for varying distances. This part of the coast is chiefly 

 within the Boreal Zone. It is extremely moist, and drenched with 

 heavy fogs during the drier season. In the main, its fauna is definitely 

 separated from that of the Boreal caps on the mountains on the 

 west of the upper Sacramento Valley by a wide stretch of semi-arid 

 Transition throughout which it is practically certain that Zapus does 

 not occur. 



Eureka probably grades into trinotatus to the northward, but at 

 just what point it is now impossible to say. There are specimens in 

 the Field Museum of Natural History from Requa and Crescent City, 

 and it is most unfortunate that they cannot be examined at this time. 

 They may be trinotatus, but for the present they are provisionally 

 referred to eureka. Similar treatment is accorded the two specimens 

 from California which were listed by Preble (1899, p. 27) under 

 trinotatus. 



