RODENTIA MURINAE HESPEROMYS PALUSTRIS. 483 



the whole foot. This is situated near the inner edge of the sole, and so far back 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 

 iburth 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. 



