HESPEROMYS. . 147 
(in skin) of 5-35, and of tail 5"-24, against his respective measurements of 4"-65 and 
4"°55. In some the tail is much more fully haired than in others. 
6. Hesperomys mexicanus. 
Hesperomys mexicanus, de Saussure, Rev. et Mag. de Zool. 1860, p. 103, pl. xi. figs. 1, La (descr. 
orig.) *. 
Hab. Mexico (de Saussure '). 
I know nothing of this species save M. de Saussure’s original description and 
Dr. Coues’s critical remarks, which will be treated of under the next species. 
Nothing has been recorded of its habits; nor does M. de Saussure mention the loca- 
lities from which his specimens were obtained. 
7. Hesperomys melanophrys. 
Hesperomys (Vesperomys) melanophrys, Coues, Proc. Ac. Philad. 1874, p. 181 (descr. orig.)*; Mon. 
N.-Am. Rodent. p. 102’. 
Hab. Mexico, Tehuacan, Tehuantepec (Sumichrast, U.S. Nat. Mus.+*). 
It is not without much doubt that I keep this species even provisionally distinct 
from the last. 
The three specimens on which Dr. Coues founded his species presented marked dis- 
crepancies from the original description of H. meaicanus, having the tail considerably 
longer than the head and body, the lower parts pure white, and the eye surrounded by 
a conspicuous black ring!2. But Dr. Coues has described three other examples, 
obtained for the Smithsonian Institution by the same collector in the same part of 
Mexico, which he himself regards as throwing great doubt on the distinction of the 
two species. Considerably smaller than either M. de Saussure’s or Dr. Coues’s types, 
these individuals want the black eye-ring, two of them have the tail shorter than the 
head and body, and one has the lower parts slightly tinged with fulvous. ‘“ Much 
more material than that now in our possession,” says Dr. Coues, “ will be required to 
determine the limits of variation of this large grey /eucopus-like Mouse of Mexico and 
to fix the species on secure basis” *. It appears to me that we have probably here to 
do with one large southern species of the subgenus Vesperomys, characterized by its 
grey fur having a peculiar hoary lustre, caused by the pale extreme tips of the hairs, 
and varying in proportional length of tail and in the presence or absence of a black 
ring round the eye. But, as I have not myself had an opportunity of comparing speci- 
mens, I refrain from definitely uniting them. 
