Did[elphys]. mes-americana Oken, Lehrbuch d. Naturgesch., pt. 3, 2:1152, 1816, type from northern México.
Didelphis mes-americana, Allen, Bull. Amer. Mus. Nat. Hist., 16:256, August 18, 1902.
Range.—Statewide.
Specimens examined, 7: nos. 100063-100067, 100074, 51396, distributed by localities as follows: Pátzcuaro (3 mi. N, 6,700 ft., 1; 2 mi. W, 6,700 ft., 2; 5 mi. S, 7,800 ft., 1), 4; Tancítaro, 1; 1-¾ mi. S Tacámbaro, 5,700 ft., 1; 1 mi. E and 6 mi. S Tacámbaro, 1.
Remarks.—The coarse overhair is white all the way to the base in three specimens but is black in its distal two thirds (white in basal third) in four specimens. The overhair, six centimeters anterior to the base of the tail, is 83 (80-85) mm. long in the three gray specimens (those with white overhair) and 68 (64-72) mm. long in the black specimens. The ears and all four feet are black. The tail is black in its proximal half and white in its distal half except in one specimen in which the distal half is almost as dark as the proximal half. Of the two largest specimens, one is a female from 1¾ mi. S Tacámbaro and the other, a male is from 6 mi. S of the same place. Measurements are: Total length, ♂ 810, ♀ 786; length of tail, ♂ 360, ♀ 348; length of hind foot, —, 58; condylobasal length, 110.0; 99.6; zygomatic breadth, 68.5; 59.6; length of nasals, 59.7, 45.0. The tail amounts to 48, 48 and 47 per cent of the total length in specimens from Pátzcuaro; 50 per cent in one from Tancítaro; 45 and 44 per cent in two from Tacámbaro. The subspecies mesamericana probably intergrades with Didelphis virginiana virginiana by way of D. m. texensis and D. v. pigra, as Davis (1944:375) and other writers suggest, in which case the proper name of the subspecies mesamericana would be Didelphis virginiana mesamericana. Until intergradation is actually demonstrated, it seems best to use the name D. m. mesamericana.
Most of our specimens were caught in steel traps, at meat baits, set for small carnivores.
Marmosa canescens canescens (Allen)
Murine Opossum; Spanish, Ratón Tlacuache
Didelphis (Micoureus) canescens Allen, Bull. Amer. Mus. Nat. Hist., 5:235, September 22, 1893, type from Santo Domingo de Guzman, Isthmus of Tehuantepec, México.
Marmosa canescens Allen, Bull. Amer. Mus. Nat. Hist., 9:58, March 15, 1897.
Range.—Below Quercus belt, probably throughout western half of state.