SACCOMYID.Z—DIPODOMYIN.E—DIPODOMYS. 539 
This second table, as far as it goes, leads to some tangible and practical 
results. More specimens would undoubtedly modify the exact figures, but 
would, I think, only confirm the general statement, that there is a decided 
difference in relative length of head and body and of tail between specimens 
from the interior and those from the coast region—just as there is in the 
genus Cricetodipus. This substautiates, in effect, the broad distinction estab- 
lished by Baird in 1857, though the details given by that author require 
qualification.* 
In the animals from the interior, with an average length of nearly 4.50 
inches, the tail is scarcely or not an inch longer than the body; that is to say, 
it is about one-fourth as long again as the head and body. 
In the coast region specimens, with an average length of less than 4 
inches, the tail is about 2 inches longer than the head and body; that is to 
say, it is, if anything, more than half as long again as the body. 
The feet do not present any very tangible characters. We find them of 
all sizes, coupled with different extremes of tail length. Nevertheless, it will 
be observed that the Cape St. Lucas specimens alone of the coast series pre- 
sent small feet, under 1.50; and that, without these, the coast series would 
show a length of foot of 1.60-1.70, thus correlated with the greater length 
of tail. 
To these data may be added some others, tending to substantiate a dif- 
ference between the two forms of the genus. The western animal averages 
smaller and of more slender build, with larger ears and longer limbs, and 
especially longer tail. It is darker in color, the prevailing tone being a mouse- 
brown, overcast with tawny or fulvous. The animal from the interior is larger, 
and noticeably more stoutly built, with smaller ears and shorter limbs, and 
particularly shorter tail. It is lighter in color, the prevailing tone being the 
*Mamm. N. Am. 1857, p. 409.—“ Whatever the number of species, all hitherto detected in North 
America belong to the two following sections :— 
“Section I. Hind foot not exceeding 1.50 inches, usually appreciably less; about one-third the 
length of head and body. Tail vertebre about 1} times the length of head and body in nature; rarely 
exceeding 5 inches, never 5}. D. ordii. 
“ Section II. Hind foot, 1.60 inches, sometimes more ; always Soacienably exceeding 1.50 ; almost half 
as long as head and body in the first specimens. ‘Tail vertebre 1% times the length of head and body, 
always exceeding 5} inches ; usually from 6 to7 inches. D. phillippi, D. agilis.” 
The proportions of body and tail here laid down I verify exactly, though the limits of extremcs 
given require to be enlarged. On the contrary, the statements made respecting the feet do not bold, 
upon examination of more material. In fact, the Cape St. Lucas are the shortest-footed animals of the 
whole seriee ; and in one very large Texas specimen (dry), not given in the table, the foot is almost 2 
inches long. 
