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14 BANGS NOTES ON DEER MICE Vol. IV 
Peromyscus leucopus ammodytes! subsp. nov. © 
Monomoy Istanp DEER MOUSE. 
Distribution — Monomoy Island, Massachusetts,— occurring, in the greatest 
abundance possible for a small mammal, on the sand-hills and in the clumps 
of beach plum and other small shrubs. We found no nests of any sort above 
ground, but numerous little round burrows in the sand, at the mouths of 
which we caught mouse after mouse as long as we kept traps set there. 
Type, from Monomoy Island, Massachusetts, adult &, no. 828, Bangs coll., 
coll. of Museum of Comparative Zodlogy, collected Dec. 28, 1893, by G. S. 
Miller, Jr., and O. Bangs. 
Characters — Rather smaller than Peromyscus leucopus noveboracensis, with 
a shorter tail—not relatively shorter, as all the proportions are about the 
same. Colors very pale,— above pale gray, below pure white to base of 
hairs. Skull small, but robust; tail, above very pale grayish, below white. 
Color.— Extreme individuals,— the type and similar specimens,— upper 
parts pale grayish fawn color, an ill-defined darker dorsal stripe drab; under 
parts pure white to base of hairs; feet and hands white; tail indistinctly 
bicolor, pale gray above, white below; ears (in dried skin) pale drab, nearly 
naked, the few short hairs silvery. 
Variations in color.— While the pale grayish specimens, with pure white 
bellies, greatly predominate on Monomoy Island, there is still a wide range of 
variation in color, and a few individuals caught with the others are not dis- 
tinguishable in any way from mainland specimens, and between these and the 
palest examples every degree of intermediate occurs. The reason for this is, 
I think, very simple. Monomoy, though often in the course of its history an 
island, has been at. other times joined to the mainland by a long beach. At 
such times skunks, cottontail rabbits and foxes have worked their way to the 
island, and have established themselves there for at least a time. The deer 
mouse from the mainland probably has come in the same way, and from time 
to time has infused into the island form the very characters it was struggling 
to eliminate. 
Miller and I tried many interesting experiments with these mice. Taking 
two, — one, a mouse similar in color to that of the mainland, and very ill 
adapted to its sandy environment, and one, the characteristic mouse of the 
island, with its highly developed protective coloration,— and placing them, 
backs up, on the sand, we would walk away from them. Very soon the gray 
individual would entirely merge into its surroundings and become invisible, 
while for a long distance more —in fact until it became too small, from dis- 
tance, to see at all—the other one would stand out in sharp outline on the 
white sand. 
1 A mmodytes — sand-burrower. 
