HOWELL — NEW BEACH MOUSE FKOM FLORIDA 
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southeastern Alabama where the conditions are practically the same 
as on Santa Rosa Island, but the series from the Alabama beaches is 
practically the same as the type series from the north side of Choctaw- 
hatchee Bay (Whitfield, Florida) The strip of beach in Alabama 
where the mice occur extends from the mouth of Perdido Bay westward 
to the mouth of Mobile Bay (the specimens being labelled “Bon Secour^* 
and “Orange Beach”); there is direct connection between the beach 
and the mainland. We have, therefore, in the case of leucocephalus a 
striking illustration of the effect of isolation in perpetuating color 
variations, and in the case of the Alabama representatives of alhifrons 
the inadequacy of a peculiar environment apart from isolation to pro- 
duce similar changes. 
Peromyscus leucocephalus sp. nov. 
WHITE-HEADED BEACH MOUSE 
Type, No. 234,358, U. S. Natl. Mus., Biological Survey collection; 9 adult, 
skin and skull, from Santa Rosa Island, opposite Camp Walton, Florida; col- 
lected February 26, 1920, by A. H. Howell; original number 2392. 
Specific characters. — Similar to Peromyscus polionotus phasma but color tone of 
upperparts drab instead of buff; colored dorsal area narrower, the whole of the 
sides white; entire head and face, except crown, white; paler, more extensively 
white, and slightly larger than Peromyscus p. albifrons. Skull similar to that of 
phasma, larger than that of alhifrons. 
Description of type. — Dorsal area, occiput, and crown light drab; rest of 
head, face, sides, underparts, and limbs white (the hairs white to base); ears 
whitish at base, becoming mouse gray at tips; tail unicolor, white, with a faint 
tinge of drab. 
Measurements. — Type: Total length, 140; tail vertebrae, 51^ hind foot, 18.5; 
ear from notch (dry), 11; average of 10 adults from type locality, 128.3; 48.4; 
18.2; 10.9. Skull (of type): Occipito-nasal length, 23.6; zygomatic breadth, 
12.3; interorbital breadth, 3.6; length of nasals, 9.1; maxillary tooth row, 3.5. 
Remarks . — This new mouse is abundant on Santa Rosa Island and 
apparently is very similar in habits to the other beach mice of this 
group. Its tracks and trails are seen everywhere among the sparse 
growth of sea oats on the ridge of dunes close to the beach and 
numerous small burrows evidently made by the mice are found in the 
face of the sand hills. A considerable number of the burrows were 
opened with a shovel but none of the mice could be dislodged. Most of 
* They average slightly paler (less brownish) on the back than typical alhi- 
frons but the heads are no more whitish. 
