1901. _Metachirus fuscogriseus pallidus_ J. A. Allen, Bull.
Amer. Mus. Nat. Hist., 14:215, July 3, type from Orizaba,
Veracruz.
1955. _Philander opossum pallidus_, Miller and Kellogg,
Bull. U. S. Nat. Mus., 205:8, March 3.
_Distribution in Tamaulipas._--Known only from along eastern
side of Sierra Madre Oriental, north to vicinity of La
Purisima.
In Tamaulipas, the four-eyed opossum is seemingly common at relatively
low elevations in the Tropical Deciduous Forest along the eastern side
of the Sierra Madre Oriental, but the species is not restricted to this
area as one specimen is available from a place seven kilometers
southwest of La Purisima, in the drier forest of west-central
Tamaulipas. The highest elevation at which individuals have been taken
in the state is approximately 2500 feet.
Specimens obtained two kilometers west of El Carrizo were caught in
steel traps that were baited with the bodies of small birds and mammals
and that were set in trails leading through a fence of piled logs that
separated a cornfield from adjacent forest. At Rancho Pano Ayuctle,
some individuals were trapped in steel sets baited with scraps of meat;
others were shot at night in the forest along the Rio Sabinas.
Schaldach reported in his notes that four-eyed opossums robbed trap
lines set for small mammals at Rancho Pano Ayuctle. W. W. Dalquest
trapped an individual seven kilometers southwest of La Purisima using
the body of an armadillo as bait. The natives of southern Tamaulipas
refer to this animal as "tlacuache cuatrojos."
Tamaulipan specimens of _P. o. pallidus_ differ from topotypes and
other specimens from the vicinity of the type locality in averaging
somewhat paler dorsally and slightly smaller in cranial dimensions when
specimens of equal age are compared. They differ also in having a
longer terminal area of white on the tail, 53.1 per cent (43.3-62.8) of
the length of the tail in 13 specimens from Tamaulipas, and 38.7
(30.9-48.2) per cent in 14 specimens from the vicinity of the type
locality of _pallidus_ in Veracruz; specimens from northern Veracruz
are intermediate between the two mentioned populations in amount of
white on the tail. Baker (1951:210) noted that the specimens from two
kilometers west of El Carrizo had "proportionately longer tails than
typical _P. o. pallidus_ from central Veracruz," but I do not find this
character to be consistent in the more abundant material now available.
_Measurements._--External and cranial measurements of three
adults, a male and female from Rancho Pano Ayuctle and a
male from two kilometers west of El Carrizo, respectively,
are as follows: 577, 580, 568; 294, 288, 290; 46, 43, 43;
40, 42, 37; condylobasal length, ----, 70.1, 69.9; palatal
length, 43.2, 42.3, 41.9; lambdoidal breadth, 23.6, 22.0,
22.7; alveolar length of maxillary tooth-row, 29.5, 28.4,
29.0.
_Records of occurrence._--Specimens examined, 15: 7 km. SW
La Purisima, 1; Rancho Pano Ayuctle, 6 mi. N Gomez Farias,
300 ft., 1; Rancho Pano Ayuctle, 25 mi. N Mante and 3 km. W
Pan-American Highway, 300 ft., 7; 10 km. N, 8 km. W El
Encino, 400 ft., 3; 2 km. W El Carrizo, 2500 ft., 3 (one
specimen deposited in Instituto de Biologia, Mexico).
=Marmosa mexicana mexicana= Merriam