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قراءة كتاب A New Pocket Gopher (Thomomys) and A New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico
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A New Pocket Gopher (Thomomys) and A New Spiny Pocket Mouse (Liomys) from Michoacán, Mexico
slightly less procumbent upper incisors. So far as we know, Thomomys umbrinus has not heretofore been reported from Michoacán. Of our seventeen skins, eight are brown, six are black and two are intermediate in color.
Most of these pocket gophers lived where there was a good growth of pine trees in the same areas where large pocket gophers of the species Cratogeomys gymnurus occurred. The field notes of the collector of the type of T. u. pullus record that when he was making a shallow excavation to reveal the gopher burrow in which he trapped the holotype, he found the burrow approximately five inches below the surface of the ground and that in digging deeper than was necessary he accidentally broke into the burrow of a Cratogeomys. Another member of our field party (E. R. Hall) when removing from its burrow a trapped Thomomys that was caught only by the hind leg, dug around the animal whose burrow was approximately six inches underground and in doing so he also broke through the roof of a burrow of Cratogeomys. The burrow of Cratogeomys was approximately sixteen inches below the ground. Nowhere else, except 3 to 5 miles south of Pátzcuaro, have the authors found two kinds of pocket gophers living together. The two-story arrangement south of Pátzcuaro was possible because of the different levels at which the two kinds of animals made their burrows and the two-story arrangement was accidental and exceptional rather than the rule.
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.
In 1943 a series of fifteen spiny pocket mice, Liomys irroratus, was obtained within a radius of five miles of Pátzcuaro and, mostly on geographic considerations, the animals were assigned to Liomys irroratus alleni (Coues). In fact, in his "Revision of the Spiny Pocket Mice," Goldman (N. Amer. Fauna, 34:57, 1911) had thus identified the one specimen available to him from Pátzcuaro. Critical examination of the series, however, revealed cranial features not described in the named kinds from adjoining geographic areas, and comparisons showed that the animal from Pátzcuaro differs subspecifically from any named kind. The new subspecies may be known as:
Liomys irroratus acutus, new subspecies
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