218 Field Columbian Museum — Zoology, Vol. III. 



specimens differ in larger size, lighter colored tail and ears, and much 

 larger skulls; while the skull of JV. d. sola is smaller generally, as 

 would be naturally expected from the difference of the body meas- 

 urements. The four specimens from Palomar, Hanson Laguna 

 Mountains, are much more heavily lined with black than the San 

 Felipe examples, and are consequently considerably darker, but I do 

 not attach any importance to this, for there is considerable variation 

 in the coloring of all these desert rats, some being much more 

 richly colored than others, sometimes verging on orange- 

 buff; others paler in the ground hue but lined heavily with black 

 so as to make them conspicuous among the rest. I am unable to 

 determine whether this difference of color is to be attributed to age 

 or is an individual peculiarity. It may be seasonal as the Palomar 

 specimens were taken in November and those from San Felipe in 

 March and April. 



MICROTUS. 

 Microtus californicus hyperythrus. 



Microtus californicus hyperythrus (misprinted huperuthrus). 

 Elliot, Pub. Field Columb. Mus., 1903, p. 161, Zoology. 



31 Specimens: 6 Aguaje de las Fresas, 8 La Grulla, 2 Vallecitos, 



3 San Antonio, San Pedro Martir Mountains; 12 San Quentin, 

 Pacific coast. 



This species at San Quentin " was found amid dense weeds and 

 grass, and at San Antonio in the thick swamp. Generally dis- 

 tributed along streams from the base of the mountains to the highest 

 meadows." 



FAM. GEOMYID/E. 



THOMOMYS. 

 Thomomys martirensis. 



Thomomys martirensis. Allen, Bull. Am. Mus. Nat. Hist., 1898, 



p. 147- 



29 Specimens: 2 Aguaje de las Fresas, 2 Vallecitos, 8 La Grulla. 



4 Santa Eulalia, 1 Santa Rosa, 1 Mattoni, 5 Parral, San Pedro 

 Martir Mountains; 6 Hanson Lagoon, Hanson Laguna Mountains, 



45 examples of Thomomys were collected by Mr. Heller, and those 

 from the higher portions of the San Pedro Martir range I have 

 separated as belonging to Dr. Allen's species. As a rule they are 

 larger than the coast animals, with longer nasals. In color they 

 vary considerably, from an ochraceous buff to dark gray, the latter 



