V i89i! V '] PROCEEDINGS OF THE NATIONAL MUSEUM. 195 



they are almost precisely like the foregoing, but do not show the black ring round 

 the eye, nor the dusky spot at the base of the metatarsus. One of them is pure white 

 below ; another is grayish (it looks as if soiled) ; while the third has the faintest 

 possible fulvous tinge all along the under parts." He says further: " Much more 

 material than that now in our possession will be required to determine the limits of 

 variation of this large, gray, leucopm-like mouse of Mexico, and fix the species upon 

 secure basis. 



In his three specimens originally referred to H. melanophrys (as 

 shown by his tables of measurements), the length of head and body 

 averages 4.02 inches and the tail 4.83, as against 3.20 and 3.10 respec- 

 tively in the other three specimens mentioned in the above quotation. 

 This difference, with the differences in coloration pointed out by Dr. 

 Coues himself, clearly shows that the latter have no close relationship 

 to H. melanophrys, but are strictly of the leucopus type. 



H. melanophrys is a large, long- tailed, big-eared species, somewhat 

 recalling the general aspect of H. caUfornicus, from which, however, it 

 differs greatly in coloration, and especially in cranial character, the 

 skull being much heavier and much broader in proportion to its length, 

 with the rostral portion greatly thickened, in comparison with the same 

 part in H. californicus. There are also well-marked differences in den- 

 tition and in the form of the palatal region ; the auditory bullae are 

 smaller and more spherical, and the condylar portion of the lower jaw 

 is much broader, heavier, and less depressed. 



Hesperomys (Vesperimus) affinis, sp. nov. 



Hesperomys (Vesperimus') melanophrys Coues, Mon. N. Am. Roden., 1877, p. 102 (in 

 part only). 



Similar to typical H. leucopus in size, proportions, and cranial char- 

 acters, but wijh a close general resemblance in coloration to H. melano- 

 phrys Coues. 



Above brownish fulvous varied with blackish, darker along the 

 median line, more fulvous along the sides. Below white, with a very 

 slight tinge of yellow. Feet dull white 5 ears brownish, narrowly 

 edged with white; tail brown, indistinctly lighter below, scantily 

 haired. 



Measurements (approximate from skins): head and body, 81.3 to 

 88.9; tail, 76 to 83; hind foot (including claws), 19.8; ear from crown, 

 4.5 to 4.8 millimeters. Skull: total length, 26.4; basal length, 25.9 

 millimeters; greatest width, 13.5; length of nasals, 11.4; lower jaw 

 (from tip of incisors to condyle), 16; height (angle to condyle), 6.4 

 millimeters. 



Type, No. flff, U. S. National Museum, $ ad., Barrio, Tehuantepec, 

 Mexico, October 30, 1868, Prof. F. Sumichrast. (This specimen presents 

 a soiled grayish appearance below, evidently accidental.) 



Two other specimens ( $ ad., No. f gf$, U. S. National Museum ; 2 ? 

 juv., No. Iflf, U. S. National Museum, same locality and collector, 

 October, 1868), are similar above, but one almost wholly lacks the faint 



