RODENTIA-MURINAE-—HESPEROMYS PALUSTRIS. 
483 
the whole foot. This is situated near tlie inner edge of the sole, and so far hack that its anterior 
extremity is scarcely more than half way from the heel to the bases of the toes. There are two 
tubercles at the bases of the second, third, and fourth toes, and one each at the bases of the first 
and fifth. The sixth tubercle, a little anterior and exterior to the posterior one, is so small as 
to be scarcely appreciable. The space posterior to and immediately alongside of the posterior 
tubercle is perfectly smooth, without granulation ; the rest of the sole is covered nearly 
uniformly with rather coarse small rounded granular tubercles, which extend a short distance 
along the bases of the toes, which beyond this are transversely furrowed. The normal tubercles 
(except the posterior) are all so small as to be with some difficulty appreciable in the surrounding 
granulation. The hind feet themselves are quite long, and set obliquely on the leg, as in the 
muskrat and some other aquatic rodents; the toes are elongated; the third is longest; the 
fourth scarcely shorter ; the second but little less ; the first claw reaches to the base of the 
second toe ; the fifth claw to the penultimate articulation of the fourth toe ; the longest toe is 
considerably more than half the distance from heel to base of the toes; there is a decided though 
slight web at the bases of the toes. 
The fingers of the fore feet are quite long, the tubercles small, as in the hind feet. The 
thumb is rudimentary, enveloped by a broad nail; the claws are shorter than those of the hind 
foot. 
The tail is nearly or quite as long as the head and body ; it is formed much as in the common 
Norway rat, the hairs, though moderately long, not concealing the annuli. 
In general appearance this animal is very similar to a half grown Norway rat, for which, at 
first sight, it would be taken by most persons. The fur, though rigid and coarse, as in Sigmo¬ 
don , is lustrous and rather compact. Above, it is of a mixed black and pale brownish ash, 
much darkened along the back by the great preponderance of black tipped or black hairs, 
grayer on the sides, the colors passing, without any very decided line of separation, into the 
ashy white of the belly. This white is of no great width, amounting, perhaps, to one-third the 
entire circumference of the body. The upper part of the tail is dusky brown ; the lower half is 
ash gray ; the upper surfaces of the feet are whitish, the hairs very lustrous. 
Specimens vary in a greater amount of yellowish brown on the sides, and with a purer white 
on the belly and feet, and a lighter shade on the under surface of the tail. 
As already stated, this species differs very greatly from Hesperomys in the much smaller ears, 
more rigid and coarse hair, and differently constituted feet. These have the hind toes longer, 
the soles entirely naked, instead of partly hairy, and the posterior tubercle greatly elongated. 
The tubercles are much smaller, but the granulations between them are much larger. The 
outer toe is much longer than in Sigmodon , reaching to the middle of the second toe instead of 
extending but little beyond its base. In Sigmodon hispidus , too, the plantar tubercles are 
larger, and the granulation does not extend beyond the bases of the toes. 
Compared with young specimens of Mus decumanus of the same size of body, the head is 
much shorter, the ears are much thinner and more membranous ; there is a distinct antitragus, 
(wanting in M. decumanus .) The feet are much more delicate, though of much the same length; 
the sides of the heel are more hairy, and the granulations under the anterior half of the meta¬ 
tarsus are entirely wanting in the Norway rat, its sole being throughout perfectly smooth. 
Specimens of this animal from western Georgia are appreciably larger than those from the 
coast, but I am unable to discern any other difference. A female from Columbus has four pairs 
of teats. 
