158 University of California Publications in Zoology I X " L - 10 



underparts pure white. In the adult pelage the hair is not so 

 silky and soft, the tail is more thickly haired, and the coloration 

 of the tail and upper parts becomes rich ochraceous-buff. 



Cranial Characters. — The skulls of P. 1. longimembris and 

 P. /. neglectus are similar in shape. Interorbital constriction 

 in the new form actually broader. The table of measurements 

 shows the dimensions of neglectus to be uniformly greater than 

 those of longimembris, and indicates that on the average the 

 ratio of the greatest mastoid breadth to the basilar length is less 

 in neglectus. 



Measurements.— As indicated above, the percentage differ- 

 ence in leading measurements is considerable. Osgood's state- 

 ment (1900, p. 13) that individual variation is not great in the 

 group does not seem to be borne out by a study of twenty-eighl 

 males of longimembris. In these the range of variation amounts 

 to 25.4 per cent of the total length, and 30.5 per cent of the 

 Length of tail vertebrae. These figures are of course subject to 

 correction, for the specimens came from different localities, and 

 some of the variation is doubtless due to age. though care was 

 exercised iii selecting the comparable adults. Stage of pelage 

 and degree of wear of the teeth were the chief characters used 

 in determining age. The fact of the comparatively large varia- 

 tion tlms reduces tlie importance of the size distinction between 

 the two forms. 



GEOGRAPHIC RANGE 



Specimens of P. I. neglectus were secured at McKittrick, 



Kern County; at Santiago Spring. Carrizo Plain. San Luis 

 Obispo County; and seven miles southeast of Simmler. San Luis 

 Obispo County. Statement of range is not possible beyond the 

 region implied in the position of these three localities, one in 

 the southwestern portion of the San Joaquin Valley, the other 

 two in the Carrizo Plain district. The subspecies is apparently 

 Lower Sonoran chiefly . though its occurrence at Santiago Spring 

 indicates that it may invade lower Upper Sonoran. 



/'. /. longimembris was taken by the Museum party at the 

 localities above mentioned (p. 156). Osgood (1900. p. 34) ex- 

 amined specimens from the following additional localities: Lodi 



