1915.] 



GEI^^US THOMOMYS. 



33 



The townsendi group also stands close to the hottse group, as shown 

 by the number and arrangement of mammae; projecting, obscurely 

 grooved incisors; and short, wide skull. 



The hottse group is large, variable, and not sharply separated from 

 the perpallidus smdfulvus groups; all of them agree in number and 

 arrangement of mammse, short ears, and many other characters. All 

 the forms except T. magdalense and T. h . russeolus are dark or light ochra.- 

 ceous, and it is doubtful whether these two pale forms may not really 

 belong to the perpallidus group, with which they agree in distinctly 

 grooved incisors. 



The alpinus group includes long, narrow-skulled, dark-colored, 

 rather large-eared forms from high up in separate mountain ranges. 

 The mammse are as in the hottse group. The incisors are abruptly 

 decurved and distinctly grooved. 



The perpallidus group includes mainly pale desert forms with very 

 small ears, but has no very distinctive group characters. The 

 incisors are abruptly decurved and distinctly grooved. 



The fulvus group includes several mountain forms of rather bright 

 tawny shades, and paler tawny valley forms in the surrounding 

 country. Some strongly resemble forms of the umbrinus group, but 

 all have the mammse in 4 pairs (2 of inguinal and 2 of pectoral) . The 

 incisors are shghtly projecting in some species. All are distinctly 

 gTOOved. 



The umhrinus group is characterized by 3 pairs of mamnise (2 of 

 inguinal and 1 of pectoral); by relatively short, wide skulls; by pro- 

 jecting, obscurely grooved incisors; and, in most species, by indented 

 or straight anterior base of zygomata. 



SLENDER ROSTRUM GROUPS. 



In the slender rostrum groups are five subdivisions, none very 

 strongly marked, but all with distinctly grooved incisors. 



The talpoides group is best characterized by 6 pairs of mammse 

 (2 of inguinal, 2 of abdominal, and 2 of pectoral), by medium-sized 

 ears, and by general gray coloration. 



Thefossor group is distinguished by 5 pairs of niammse (2 pairs of 

 inguinal and 3 of pectoral) and by generally brownish coloration, 

 jl In the three mountain forms the ears are rather large, but in the two 

 ! vaUey forms (T. quadratus and T.fisJieri) the ears are very small. 



The douglasi group and the two following are distinguished by 4 

 j pairs of mammse (2 of inguinal and 2 of pectoral). 

 ! The monticola group is very similar to the douglasi group, but has 

 j shghtly larger and more pointed ears and generally more slender 

 j skulls. 



The fuscus group is distinguished by very small, pointed ears and 

 light brown color. 



I 98121°— 15 3 



