align="right">216

111 35.9 36.4 21.7 19.6 3.6 13.8 12.1 23.0 Maximum 222 113 37    36.9 22.1 20.7 3.8 14.2 12.5 23.5 Minimum 210 109 34    35.9 21.3 19.1 3.3 13.4 11.6 22.1 D. o. sennetti, 2 mi. S Riviera, Texas (after Setzer, op. cit. :565) Mean (5) 218 112 35.8 37.2 23.4 20.1 4.0 13.6 13.1 24.2 Maximum 222 115 38    38.2 24.1 20.7 4.3 14.4 13.2 24.6 Minimum 208 104 34    36.3 23.0 19.4 3.8 13.0 12.6 23.8

Dipodomys ordii largus new subspecies

Ord Kangaroo Rat

Type.—Female, adult, skull and skin, No. 27234, Mus. Nat. Hist., Univ. Kansas, from Mustang Island, 14 mi. SW Port Aransas, Aransas County, Texas; obtained 30 June 1948 by W.K. Clark; original No. 543.

Range.—Known from Mustang Island only.

Diagnosis.—Size medium (see measurements). Color pale, and as described for D. o. parvabullatus. Skull small; auditory bullae (actually and relative to remainder of skull) smaller than in any other known kind of Dipodomys, except D. o. parvabullatus in which breadth across bullae is approximately the same; notably narrow across maxillary processes of zygomatic arches.

Comparisons.—From Dipodomys ordii sennetti (J.A. Allen) of the mainland, D. o. largus differs in: Color paler on pigmented areas; white areas more extensive; skull averaging smaller except in basilar length and length of nasals which are approximately the same as in D. o. sennetti. From Dipodomys ordii compactus True of Padre Island, D. o. largus differs in: Body longer; tail shorter; skull narrower across tympanic bullae and across maxillary processes of zygomatic arches; nasals shorter. From Dipodomys ordii parvabullatus of the coastal island south of Padre Island, along the gulf coast of Tamaulipas, D. o. largus differs in: Body and tail longer; basilar length of skull averaging less; breadth across maxillary processes of zygomatic arches greater; premaxillae not extending so far behind nasals.

Remarks.—D. o. largus resembles D. o. compactus in external proportions and D. o. parvabullatus in cranial proportions. The degree of difference between D. o. compactus and D. o. largus is less than between D. o. compactus and D. o. parvabullatus. To me, the three subspecies mentioned in the preceding sentence are indistinguishable in color.

Two of the eleven specimens of D. o. largus are of the light color phase (upper parts Cartridge Buff) whereas all but two of the eleven specimens of D. o. compactus are of the light color phase. Each of the cheek-teeth of the upper jaw of D. o. largus has a complete ring of enamel around the dentine of the occlusal surface, as described by Setzer (Univ. Kansas Publ., Mus. Nat. Hist., 1:517, December 27, 1949) for D. o. compactus. The upper dentitions of ten specimens of D. o. compactus examined by me in this respect reveal a total of only five teeth (in four individual animals) that have the enamel ring incomplete; one premolar and three molars are incomplete on the lingual side and one molar is incomplete on the labial side.

Two specimens from Bagdad, Tamaulipas, in the delta of the Río Grande (Nos. 116485 and 11487, U.S.N.M., Biol. Surv. Coll.), are referred to D. o. compactus on basis of long body and long tail. The specimens, both Light Ochraceous-Buff, are so young that not all of the enamel is worn off the crowns of the cheek-teeth. Specimens of D. o. compactus, D. o. parvabullatus and D. o. sennetti of comparable age are not available, and it, therefore, is impossible to know whether size and shape of the skull in the population at Bagdad are the same as they are in D. o. compactus of Padre Island.

Specimens examined.—Total, 11, all from Texas. Aransas County: Mustang Island, 14 mi. SW Port Aransas.

Sigmodon hispidus solus new subspecies

Hispid Cotton Rat

Type.—Male, adult, skull and skin; No. 35468, Mus. Nat. Hist., Univ. Kansas; from island, 88 mi. S and 10 mi. W Matamoros, Tamaulipas, Mexico; 22 March 1950; obtained by E.R. Hall and Curt von Wedel; original No. 6806 E.R. Hall.

Range.—Known from the type locality only but probably occurring on most of the chain of islands off the coast of Tamaulipas.

Diagnosis.—Small; hind foot short; rostrum broad.

Comparison.—From its nearest relative, geographically and morphologically, Sigmodon hispidus berlandieri Baird of the adjacent mainland, S. h. solus differs in smaller size, and a rostrum that is broader in relation to the length of the skull.

Remarks.—On the last night of our stay on the island, traps set in grass approximately 20 inches high, yielded one pair of Sigmodon. The color is lighter than in the average of specimens from the mainland (for instance those from Victoria and Soto la Marina) but can be matched by selected specimens. In animals of equal age, the hind foot and basilar length are shorter in S. h. solus than in berlandieri. The broadening of the rostrum, which occurs with advanced age, is attained in solus when the skull is yet short; the maximum breadth of the rostrum in the adults is more, instead of less, than a fourth of the basilar length.

Measurements.—The following measurements are of specimens in which the occlusal face of each molar tooth is worn flat. The first measurement is of the holotype followed by the corresponding measurement of a male of T. b. berlandieri, No. 116466 from Camargo, Tamaulipas, in parentheses. The third measurement is that of the female from the type locality of S. h. solus and it is followed by the corresponding measurement of a female of T. b. berlandieri, No. 116462 from Camargo, Tamaulipas. Total length, 266 (298),—(293); length of tail, 113 (135),—(137); length of head and body, 153 (163), 155 (156); length of hind foot, 30 (35), 30 (33); basilar length of Hensel, 28.2 (28.9); 27.9 (29.0); zygomatic breadth, 19.5