4/0 University of California Publications in Zoology [Vol.12 



number of intergrading forms and of individuals is greater than in any 

 similar group of mammals known. From typical maniculatus, development 

 may be traced step by step absolutely without break through all the numerous 

 subspecies (Osgood, 1909, p. 41, and frontispiece). 



Here we have a spectacular illustration of the principle that the 

 closest relative of any form is found, not in a locality far distant nor 

 in a locality identical with that occupied by the form, but in a neigh- 

 boring region separated from the first by a barrier of some sort 

 (see p. 464). 



Respecting the Californian forms of the genus Onychomys it may 

 with all assurance be said that no two species are found in one 

 locality. This genus has recently been revised by Hollister (1914, 

 pp. 427-489). 



The distribution of the Murid genera Eeithrodontomys, Sigmodon, 

 Neot&ma, Evotomys, Microtias, and Fiber, as well as of the genus 

 Peromyscus, afford a mass of material similar to that which has 

 alreadv been adduced. 



Zapus trinotatus trinotatus ranges from the coast region of south- 

 ern British Columbia, Washington (including Cascades), Oregon 

 (west of western base of Cascades), to northern California, being 

 found as far south as Carson's Camp on Mad River, Humboldt County. 

 Its closely related subspecies Zapus trinotatus alleni (Preble, 1899, 

 pp. 27. 2S) occupies the Boreal zone of the Siskiyou. Trinity, and 

 Sierra Nevada mountains, as well as the inner coast range as far 

 south as South Yolla Bolly Mountain (between Tehama and Trinity 

 counties) . 



Zapus major is probably an outlying form with trinotatus affini- 

 ties (Preble, 1899, p. 25). It is found on the Warner Mountains of 

 Oregon and California. Zapus orarius is found in the humid coast 

 belt of California from Marin County to Humboldt Bay. Its rela- 

 tionships are not clear, but it is probably nearest to Zapus pacificus, 

 which is found in the interior valleys of southwestern Oregon and 

 northwestern California. 



Aplodoxtiidae 



Although detailed facts regarding the aplodontias are not so 

 numerous as is desirable, it seems obvious that the relationships of the 

 California forms are as follows: The recently described Aplodontia 

 chryseola (Kellogg. 1914. pp. 295, 296) occupying the Trinity and 



