FAMILY MURIDS. 
91 
A. imttali. (Harlan, Med. and Phys. Res. p. 55, plate.) Fawn color above, white beneath; ears 
large and hairy. Tail nearly as long as the body. Length 5| inches. Virginia. 
A. pinetorum. (Le Conte, Ann. Lyc. Vol. 3, p. 132, plate.) Dark ash, tipped with brown; ears 
short, naked, concealed; thumb with a straight nail. Tail round, 0 • 7 long. Length 3 to 4 inches. 
Georgia. 
A. gapperi. (Zool. Joum. Vol. 5, p. 202.) Tail more than half the length of the body; ears short, 
rounded, chesnut above ; face and sides yellowish brown ; belly yellowish white; chin and throat 
ashen. Tail nearly two inches. Length six. An neoboracensis ? 
A. ferruginous. (Harlan, Med. and Phys. p. 57.) Rust-colored above, white beneath; fore legs 
short. Tail more than half the length of the body. Length 11 inches. Mississippi. 
A. richardsoni, ( riparius of Richardson, p. 120.) Dull brown mixed with black, bluish grey beneath; 
ears moderate, nearly concealed. Tail flat, as long as the head ; feet white. Length 9 inches. 
Arctic Regions. 
A. rubricatus. (Beechey’s Appendix.) With a bright red stripe on the flanks. Behring's Straits. 
Genus Neotoma, Say and Ord. Molars with large roots; the folds of the enamel not descending as 
low as the edge of the alveolar processes. Its other characters similar to the genus Arvicola. 
N. floridanum. (Ac. Sc. Vol. 4, p. 345, pi. 21.) Plumbeous above, yellowish on the sides; eyes and 
ears very large. Tail longer than the body. Length 14 inches. Florida. 
N. drummondi. (Richardson, pi. 7.) Yellowish brown above, white beneath. Tail more bushy 
towards the extremity, longer than the body. Length 16 inches. Rocky Mountains. 
Genus Sigmodon, Say. Molars subequal, with roots; the folds of the enamel representing the letter S. 
S. hortense. (Harlan, Med. and Phys. pi. Ac. Sc. Vol. 4, pi. 22.) Soiled yellow or blackish above, 
beneath cinereous; ears large and round. Tail nearly as long as the body. Length 10 inches. 
Florida. 
Genus Georychus, Illiger. Eyes very small; ears rising slightly above the auditory hole; thumb 
obvious ; toes of the fore feet formed for digging. Tail very short. 
G. helvolus. (Richardson, p. 128.) Head black and tawny; body reddish orange, paler beneath. 
Length 5 inches. Northern Regions. 
G. trimucronatus. (Richardson, p. 130.) Chesnut above ; thumb nail with three projecting points. 
Length 5£ inches. Arctic Regions. 
G. hudsonius. (Id. p. 132.) Dark brown above, bright rusty on the sides; the two middle nails of 
fore feet very large, with a deep notch on the ends ; earless. Length 6 inches. Labrador and 
Arctic Regions. 
G. grccnlandicus. (Id. p. 134.) Earless; a dark dorsal stripe; nails of the forefeet terminating in 
sharp cylindrical points. Length 7 inches. Arctic Regions. 
Genus Aplodontia, Richardson. Molars ten above, eight beneath; ears short and round; feet five¬ 
toed ; nails large, strong and compressed. Tail minute, concealed by the fur. 
A. leporina. (Richardson, p. 211, pi. 18.) Umber brown above, greyish beneath; legs short; throat 
with a white spot. Tail i an inch. Length 14 inches. Northern Regions, Missouri. 
