2 University of California Publications in Zoology [Vol. 21 



The races which inhabit chiefly or exclusively marshes, aestuarinus, 

 vallicola, and scirpensis, are characterized by blackish color of the 

 upperparts. The subspecies which inhabit the higher foothill areas, 

 huperuthrus, neglectus, and mariposae, show a tendency to become 

 reddish. One race, constrictus, is a notably depauperate form. 



The color-names used in this paper are taken from Ridgway's 

 Color Standards and Color Nomenclature (1912). All color descrip- 

 tions were made by inclining the trays of specimens at an angle of 30° 

 in reflected light. In this way it was thought that uniformity could 

 be secured in judging of the tones in mass effect. It was very difficult 

 in most cases to determine the exact shade of color, owing to the con- 

 fusing presence of the dark overhairs, the lighter tips of the shorter 

 hairs, and the basal portions of the fur which show through. 



The measurements of the skulls were all taken with steel calipers 

 graduated to tenths of millimeters. Total length, tail vertebrae and 

 hind foot are as taken by the field collectors. 



ACKNOWLEDGMENTS 



The present paper includes the results of a part of the work done 

 in the Department of Zoology of the University of California, toward 

 securing the degree of doctor of philosophy. Material additional to 

 that in the Museum of Vertebrate Zoology was loaned by the Field 

 Museum of Natural History, the Bureau of Biological Survey of the 

 United States Department of Agriculture and the United States 

 National Museum. For use of these specimens the writer is indebted 

 to Mr. Wilfred H. Osgood, Mr. E. W. Nelson, and Mr. Gerrit S. 

 Miller, Jr., of these three institutions, respectively. To Dr. Joseph 

 Grinnell, Director of the Museum of Vertebrate Zoology, the writer is 

 indebted for the use of the collection and of museum records in his 

 charge, as well as for advice from time to time and assistance in bring- 

 ing this paper into final form for publication ; also to Messrs. Harry S. 

 Swarth and Joseph Dixon, of the Museum staff, for help in many 

 ways. 



LIST OF SUBSPECIES OF MICBOTUS CALIFOENICUS, WITH 

 TYPE LOCALITIES 



Microtus calif ornicus calif ornicus (Peale). San Francisco Bay [near Palo 

 Alto], California. 



Microtus calif ornicus constrictus Bailey. Cape Mendocino, Humboldt County, 

 California. 



Microtus californicus eximius, new subspecies. Near Mount Sanliedrin, Men- 

 docino County, California. 



