MURIDAIX—SIGMODONTES—HESPEROMYS MICHIGANENSIS. 95 
to the prairie”; that is to say, the differences detailed by these authors are 
simply and exactly dependent upon whether the animal lives in woodland or 
in prairie. 
As will be seen by the table below, HL. michiganensis is much smaller 
than /eucopus, averaging under three inches long (2.95), and only exception- 
ally, in extreme cases, reaching the average dimensions (34) of Jeucopus. 
Some adult examples, indeed, are hardly over 24 in length. The next most 
conspicuous feature is the uniformly shorter tail, both relatively and absolutely. 
With an average of just two inches, it ranges from 13, or a little less, to 24, 
but is hardly ever over 24, and not very often below 2. In general, it about 
equals the head without the trunk, having, therefore, much the same relative 
strength as in H. var. sonoriensis. The smallness of the feet is equally 
marked and characteristic. The very largest hind feet do not exceed 0.75, 
which is below the average of /eucopus ; they range between 0.65 and 0.75, 
settling at 0.69 for the mean size. As it is rare for the smallest foot of deu- 
copus to drop to 0.75, this feature alone gives indications by which probably 
nineteen specimens of every twenty could be identified. The ears are notice- 
ably short and small every way; usually under 0.50 high, they run from 0.40 
to 0.50, only very rarely surpassing the latter figure. 
The coloration is almost equally distinctive in its uniform darkness. Most 
of the specimens come nearest to “‘austerus” in this respect. The dark color 
almost always* extends on both feet to the digits, whereas in dewcopus the feet 
are (usually) white. The shade is difficult to name, but may be called a mix- 
ture of gray and yellowish-brown on the sides, passing along the middle line 
of the body above, from nose to tail, as a broad stripe, into blackish-brown. 
The under parts are snow-white. ‘The tail is always distinctly bicolor, and 
usually sharply so, but sometimes the under surface is brownish-white. The 
ears are blackish, usually without the slightest pale edging. ‘The whiskers 
are light and dark, and the longer ones exceed the head 
This animal is stated to have six mamma—four abdominal and two pec- 
toral. The label upon one of Mr. Kennicott’s infant specimens says, “five 
found together.” On the label of another of his, he states that “two old ones, 
with three young, were found in a rail-fence on the prairie.” 
Aside from the question of ‘“bairdii”, which must be summarily disposed 
* A Kansas specimen, which I refer to this species, forwarded for examination by Prof. FP. H. Snow, 
presents the exceptional feature of nearly white feet; the dusky color of the legs only reaching a little 
way past the gnkle, and not at all beyond the wrist. 
