72 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
leucopus, and this is particularly evident in those from the open, dryer parts 
of Southern California, and especially such examples as No. 7185 from the 
Colorado Desert region, where the coloration is a brisk fulvous, without dorsal 
stripe. But nearly all the specimens can be matched by eastern examples ; 
and, moreover, all the northern ones are actually darker than average /eucopus, 
while most of them show a distinct dorsal stripe. “The entire outside of the 
fore leg below the shoulder white?” Ina part of the specimens this is so, and in 
another part of the specimens it 1s not so; and the same is the case with ordi- 
nary leucopus. It is evident, therefore, that the characters ascribed to the 
supposed ‘‘gambeli” fall to the ground. 
Passing now to another Pacific-coast species, so-called, we will premise 
that in establishing his 7. ‘‘austerus”, Professor Baird intimated his suspicion 
that it might not prove valid. ‘It is barely possible,” he says, “that my HZ. 
austerus may be a northern variety of the common Californian species” (A. @., 
“oambeli”), ‘of smaller size and darker color, somewhat like the gray and 
smaller H. /eucopus of Nova Scotia and probably Labrador, * * and further 
materials will be necessary to decide the question.” With the necessary addi- 
tional material before us, we cannot only confirm the suggestion here made, 
but we can also show a perfect intergradation between “gambeli” and “aus- 
terus”; a melting of this last into “‘boylii”; and, finally, the positive identity 
of ‘“boylii” with ‘“myoides”, which last we have proved to be the same as 
leucopus. 
The Simiahmoo specimens, which are, as we have just shown, referable 
‘“oambeli” from the dry, open parts 
to ‘‘gambeli”, are so much darker than 
of California, that they stand rather nearer ‘austerus” in color than to 
the former examples of the species they are supposed to belong to! 
Color thus giving us nothing tangible, we will interrogate dimensions, and see 
if these show anything of specific value. We accordingly present a short 
table; most of our samples of supposed “austerus” being immature, and 
therefore excluded as tending to vitiate the result. 
