A New Pocket Gopher (Thomomys) and A New

Spiny Pocket Mouse (Liomys) from

Michoacán, Mexico

Type.—Male, adult, skin and skull; No. 100151, Univ. California Mus. Vert.
Zool.; 5 mi. S Pátzcuaro, 7800 ft., Michoacán, Mexico; March 10, 1943; obtained
by Hubert H. Hall, original No. 117.

Range.—Known only from 3 to 5 miles south of Pátzcuaro, Michoacán.

Diagnosis.—Size small (see measurements); color black or between Cinnamon-Brown
and Snuff Brown; distal half of tail whitish and all of tail whitish
in one specimen; lambdoidal crests perpendicular to sagittal plane of skull;
posteroventral face of tympanic bulla rugose; jugal vertical (flat surface not
oblique); interpterygoid space truncate at apex with sides curved outward
(see figure).

Comparison.—From topotypes of Thomomys umbrinus supernus Nelson and
Goldman, pullus differs as follows: More individuals wholly black (except
distal half of tail); underparts lacking white; rostrum broader; braincase anteriorly
slightly more expanded dorsally; lambdoidal crests perpendicular to
sagittal plane rather than inclined posteromediad; interparietal broader, 5.7
(5.0-7.0) versus 4.5, and in 6.5 (5.6-7.1) rather than 4.8 (4.4-5.1); flattened
middle part of jugal vertical rather than oblique; in side view, mastoid and
paroccipital processes farther apart thus exposing larger surface of mastoidal
bulla; incisors, in both upper and lower jaws, slightly narrower; molariform
teeth smaller, interpterygoid space truncate, at apex, with sides convex mediad,
rather than V-shaped; ventral face of tympanic bullae rugose in posterior half
rather than smooth.

Measurements.—Average and extreme measurements of five adults of each
sex, are as follows: Total length, male 184 (178-198), female 185 (174-194);
length of tail, 54 (48-60), 53 (47-57); length of hind foot, 26.8 (25-29), 27.6
(26-29); weight, 86.1 (78.7-96.9), 74.3 (70.2-84.8) grams; basilar length, 30.2
(28.8-31.3), 28.6 (27.8-29.1); zygomatic breadth, 23.2 (22.3-24.6), 21.3 (20.8-21.8);
least interorbital breadth, 5.9 (5.8-6.1), 6.4 (6.0-6.8); mastoid breadth, 17.8
(17.1-18.7), 17.2 (16.6-17.5); length of nasals, 12.4 (11.8-13.0), 11.5 (11.0-12.5);
breadth of rostrum, 7.5 (6.9-8.2), 7.1 (6.9-7.3); length of rostrum, 14.1 (13.4-14.5),
13.3 (12.7-13.5); alveolar length of maxillary tooth-row, 7.0 (6.7-7.5), 6.9 (6.8-7.0);
palato-frontal depth, 13.2 (13.0-13.4), 12.9 (12.3-13.5).

Specimens examined.—Total, 17, all from 7800 ft., Michoacán, as follows:
3 mi. S Pátzcuaro, 1; 4 mi. S Pátzcuaro, 10; 5 mi. S Pátzcuaro, 6.

Type.—Female, adult, skin and skull; No. 100171, Univ. California Mus.
Vert. Zool.; 2 mi. W. Pátzcuaro, 7700 ft., Michoacán, Mexico; March 10, 1943;
obtained by E. R. Hall and J. R. Alcorn, original No. 3837 of Alcorn.

Range.—Known only from the vicinity of Pátzcuaro, Michoacán.

Diagnosis.—Size large (see measurements); upper parts dark brown; posterior
border of nasals V-shaped with apex directed anteriorly; frontomaxillary
suture medially concave or rarely straight; interparietal subcircular; basisphenoid
wide; tympanic bullae large.

Comparisons.—From Liomys irroratus alleni, acutus differs as follows: Color
slightly darker brown on upper parts; size slightly less; posterior border of
nasals V-shaped rather than truncate; frontomaxillary suture medially concave
or straight instead of convex; interparietal subcircular (anterior border) rather
than triangular; basisphenoid broader; tympanic bullae larger and more inflated.
From Liomys irroratus jaliscensis (topotypes), acutus differs as follows:
Color slightly darker brown on upper parts; size larger, without overlap, in
external measurements and in basilar length, length of nasals and mastoid
breadth; posterior border of nasals V-shaped rather than almost truncate;
frontomaxillary suture medially concave or straight rather than convex; interparietal
subcircular rather than quadrilateral; basisphenoid wider; tympanic
bullae larger. From Liomys irroratus pullus, acutus differs in longer body,
shorter tail, slightly longer hind foot; all of upper parts, and especially upper
side of tail, more brownish and less blackish; posterior border of nasals and
frontomaxillary suture differing in same way as from alleni; interorbital region
narrower in relation to length of skull; over-all length of skull greater; interparietal
anteroposteriorly longer; tympanic bullae more inflated.

Measurements.—The measurements of two males, Nos. 100184, 100182, and
average and extreme measurements of five females, are, respectively, as follows:
Total length, 257, 267, 244 (230-251); length of tail, 130, 128, 122 (105-129);
length of hind foot, 32, 31, 31 (30-33); length of ear from notch, 16, 17,
15.3 (13.0-19); weight in grams, 71.5, 65.1, 50.8 (44.8-61.8); greatest length of
skull, 35.2, 34.9, 33.6 (32.7-34.2); zygomatic breadth, 17.7, 17.5, 16.5 (16.1-17.1);
interorbital breadth, 8.4, 8.1, 7.8 (7.5-8.0); length of nasals, 15.1, 14.9, 14.0
(13.3-14.5); width of braincase, 15.9, 15.1, 15.0 (14.7-15.1); alveolar length of
upper molariform tooth-row, 6.0, 6.0, 5.6 (5.5-5.9). The measurements were
taken according to the method of Goldman (N. Amer. Fauna, 34:10, 1911).
Each of the specimens of which measurements are given above is adult; the
transverse enamel fold has been obliterated in M1, is represented by only an
isolated lake in M2 (except in one female where all trace of the fold has worn
away) and is present in M3.

Specimens examined.—Total, 16, all from Michoacán, Mexico, and unless
otherwise indicated in the University of California Museum of Vertebrate
Zoölogy, as follows: 3 mi. NW Pátzcuaro, 6700 ft., 1; 2 mi. W Pátzcuaro,
7700 ft., 5; 2 mi. W Pátzcuaro, 6700 ft., 2; Pátzcuaro, 1 (U. S. Nat. Mus.);
5 mi. S Pátzcuaro, 7800 ft., 7.