454 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



SlcuU. — Almost precisely like the skuU of longipes. Compared with 

 skulls of arcticejJS it is narrower, longer, and more arched, with longer 

 rostrum and longer, higher braincase. I can find no character to 

 separate the skuUs from those of longipes. There is, perhaps, less 

 tendency toward the development of a spine on the posterior border 

 of the palate, but in the leucogaster group this character is exceedingly 

 variable and veiy unreHable. 



Measurements. — Type and averages, the latter in parentheses, of 

 seven adults from Kansas and Oklahoma: Total length, 164 (156); 

 tail vertebrse, 42 (42); hind foot, 21.0 (22.0); ear from notch in dry 

 skin, 13.2 (12.8). Skull: Condylobasal length, 27.4 (26.9) ; zygomatic 

 breadth, 15.1 (15.3); interorbital breadth, 4.4 (4.7); breadth of 

 braincase, 12.5 (12.9); length of nasals, 11.5 (11.6); length of man- 

 dible, 15.9 (15.7) ; maxiUary tooth row, 4.7 (4.6). For detailed meas- 

 urements of specimens see page 479. 



Type-specimen. — No. ||-Hf> United States National Museum. 

 Skin and skull of adult female (teeth moderately worn). Collected at 

 Fort Reno, Oklahoma, February 16, 1890, by Dr. J. C. Merrill. 

 Original number, 18. 



Remarks. — This subspecies intergrades with 0. 1, arcticeps. Speci- 

 mens from Paladora Canyon, Texas, though placed with arcticeps, are 

 undoubtedly intermediates. Skulls of specimens from Neligh, 

 Nebraska, show an approach toward skulls of arcticeps in a general 

 shortening and flattening, but the skins are typical of hreviauritus. 

 Intergradatiou doubtless takes place also with longipes, which the 

 Oklahoma form most resembles in general characters, but specimens 

 to connect the ranges of the two subspecies throughout southern 

 Oklahoma and north-central Texas are wanting. 



Specimens examined. — Total number 41, from locahties as foUows: 



Nebraska: Neligh, 8. 



Kansas : Fort Riley, 1 ; Neosha Falls, 1 (^lus. Comp. Zool.); 

 Kinsley, 1. 



Oklahoma: Alva, 17; Beaver River, 5 (Amer. Mus. and Field 

 Mus.) ; Camp Supply, 1^ ; Fort Reno, 4; Neutral Strip, 1 (Amer. Mus.); 

 White Horse Springs, 1 (Field Mus.); Woodward, 1. 



ONYCHOMYS TORRIDUS (Coues). 

 (Synonymy under subspecies.) 



Diagnosis. — Compared with OmjcJiomys leucogaster, this species 

 averages smaller and lighter built, with relatively longer tail (usually 

 more than half the length of head and body). The skuU averages 

 considerably smaller and less stoutly built, but with the interorbital 

 region comparatively wide. The teeth are lower crowned, the 

 unworn cusps of m^ longer than high, or with these dimensions 



1 Skeleton only. 



