Type.—Female, adult, no. 262655, U. S. Nat. Mus. Biol. Surv. Coll.; Bird Island, Great Salt Lake, 4,300 ft., Tooele County, Utah; obtained on June 22, 1937, by W. H. [Marshall], X-catalog no. 27969.
Range.—Bird, Carrington, Badger and Stansbury islands, Great Salt Lake; around western edge of Great Salt Lake north to Kelton, Box Elder County, Utah; around southern and southeastern edge of the lake to mouth of the Jordan River; marginal occurrences are: all in Utah, Kelton, 2 mi. W Grantsville, 14 mi. W Salt Lake City and Bird Island, Great Salt Lake.
Diagnosis.—Size medium (see measurements). Color pale, entire dorsal surface near Pinkish Buff, purest on sides, flanks and cheeks with but slight suffusion of black on upper parts; arietiform markings, pinnae of ears, plantar surfaces of hind feet, and dorsal and ventral stripes of tail, brownish. Skull medium in size; rostrum narrow and long; pterygoid fossae ovoid; cutting edge of upper incisors narrow; external auditory meatus round and small; jugal straight or nearly so.
Comparisons.—From Dipodomys ordii pallidus, D. o. marshalli differs in: Hind foot smaller; color darker, arietiform markings more distinct; dorsal and ventral stripes of tail more pronounced; skull smaller; palate shorter and wider; jugals lighter; external auditory meatus smaller; cutting edge of upper incisors narrower; nasals shorter and less flared distally.
From Dipodomys ordii utahensis, D. o. marshalli differs in: Size smaller; color lighter; skull smaller, except least interorbital width and depth of auditory bullae which are greater; cutting edge of upper incisors narrower; nasals less flared distally.
For comparison with Dipodomys ordii celeripes see account of that subspecies.
Remarks.—This subspecies was described from Bird Island, Great Salt Lake, and was thought by [Marshall] (1940:153), who collected the specimens, to be restricted to that island. However, specimens taken over a period of years on the nearby mainland, by students from the University of Utah, are referable to this subspecies. Although these animals from the mainland are referable to D. o. marshalli, they have some characteristics of D. o. utahensis from the eastern and southern mainland. Four specimens from Kelton, also on the mainland, are not typical of D. o. marshalli; nevertheless, more than half of their characters of taxonomic worth are as in D. o. marshalli to which the animals are referred.
Great Salt Lake has not been so effective in isolating the animals living on the islands as heretofore has been thought. After these supposedly isolated kinds of animals from Great Salt Lake were named, some other workers have shown several of the kinds to have extensive ranges on the mainland. Some of the kinds ranging also on the mainland are: Dipodomys ordii marshalli, Dipodomys microps subtenuis and Peromyscus crinitus pergracilis. Of the animals named from the islands, I suppose that those which require the semiarid habitat found in this area will all be found to have large ranges on the adjacent mainland and that each of the kinds of animals which do not require the above habitat, and which lived in this region during the Pleistocene, will be found to be restricted to the island from which it was named.
Specimens examined.—Total, 47, all from Utah, distributed as follows: Box Elder County: Kelton, 4300 ft., 7 (5 MVZ; 2 UU). Tooele County: 2 mi. W Grantsville, 1 (CAS); Bird Island, Great Salt Lake, 4300 ft., 1 (USNM); Carrington Island, Great Salt Lake, 4300 ft., 1 (USNM); Stansbury Island, Great Salt Lake, 4300 ft., 10 (6 UU; 4 USNM). Salt Lake County: 18 mi. W Salt Lake City, 4260 ft., 16 (UU); 17 mi. W Salt Lake City, 4320 ft., 7 (UU); 16 mi. W Salt Lake City, 4300 ft., 3 (UU); 14 mi. W Salt Lake City, 4300 ft., 1 (UU).