MURIDA—SIGMODONTES—NEOTOMA CINEREA. 27 
ones form a brush ¢wo inches beyond the end of the vertebrae. This maxi- 
mum of hairiness, however, is rarely if ever seen, except in boreal specimens : 
the most heavily-haired United States tails are only about two inches across ; 
an average one is rather less than this; the average pencil at the end is prob- 
ably not over one inch. There is a great difference, also, according to season. 
In the spring, when the animal has just lost its heavy winter-coat; and in 
summer, before it has commenced to put on its protection from the cold, the 
tail may be only a little more hairy than in Kansas samples of JV. floridana. 
Thus, in Nos. 3897, 3898, 9324, &c., the hairs are much less than an inch 
across, along most of the tail; and this member looks precisely as figured by 
Audubon. Comparison of Audubon’s with Richardson’s plates will give an 
excellent idea of the extreme differences ; both these figures are faithful, and 
can be precisely matched in our series. It is hardly necessary to add that, 
nevertheless, the tail is never so scant-haired as to permit the annuli to be 
seen. 
The ears, and to some extent the feet, share the general increase of hair- 
iness over floridana that the tail shows. The ears are, in general, closely and 
softly pilous, much like a squirrel’s; never so nearly naked as in floridana, &c. 
In United States specimens, there is not much difference in this respect ; but, 
in the arctic ones, this soft pilous state becomes actually hirsute. In all the 
specimens, the heels are closely hairy to the posterior tubercle ; in arctic ones, 
the hairiness is more dense, and even encroaches on the sole from the sides. 
The hairs on the upper surfaces of the toes generally reach about to the ends 
of the nails; in arctic examples, they are longer, completely hiding the 
claws. The palms are always completely naked from the posterior tubercles. 
The tubercles are five in number: two abreast, posterior; two abreast at base 
of 5th and 2d toes, respectively; one intermediate between these last and a 
little anterior to them at conjoined bases of 3d and 4th digits. The very 
rudimentary 1st digit looks exactly like an additional tubercle at the antero- 
internal corner of the inner posterior one. The soles have six tubercles, 
with the ordinary disposition; the posterior one of these is subcircular (not 
linear, as in Mus, &c.). 
Aside from seasonal conditions, which, being well known, and the same 
as in other rodents, need not be here particularized, the pelage varies in the 
series as follows: The arctic skins are very full-haired and soft; the United 
States prairie-region skins are equally soft, if not more so, but not so full ; 
