Part 91

Characters for ready recognition.--Differs from Mustela africana stolzmanni by absence of median, longitudinal, abdominal stripe of same color as upper parts, presence of p2 and two roots rather than one root on P2; from Mustela frenata macrura by darker color (Carbon Brown, tone 3, pl. 342 rather than Chocolate, tone 3, pl. 343, Oberthür and Dauthenay) of upper parts.

Description.--Size.--Male: Measurements of the type specimen and topotype, no. 24132, are, respectively, as follows: Total length, 382, 418; length of tail, 152, 164; length of hind foot, 52, 48. Tail 66 and 65 per cent as long as head and body. Hind foot more than basal length.

Female: Measurements of two referred females, no. 24134 from Ambo and no. 24136 from Huanuco, are, respectively, as follows: Total length, 328 and 303; length of tail, 118 and 103; length of hind foot, 39 and 38.5. Tail 56 and 51 per cent as long as head and body. Hind foot shorter than basal length.

The average differences in external measurements of the two sexes are: Total length, 85; length of tail, 49; length of hind foot, 11.

Externals.--Longest facial vibrissae black and extending beyond ear; carpal vibrissae same color as upper parts and extending to apical pad of fifth digit; hairiness of foot-soles as shown in figure 20.

Color.--Rarely a few white hairs anterior to each ear; posterior fifth of each upper lip white; top of head, posteriorly to slightly behind ears, black, grading into color of upper parts of body; dark spots at angles of mouth absent; tip of tail black; remainder of upper parts near (n) Argus Brown and Carbon Brown, tone 3 (pl. 342, Oberthür and Dauthenay); chin whitish; remainder of underparts Warm Buff; color of underparts extends distally on posterior sides of forelegs to wrists but not reaching foot-soles and on hind legs to slightly below knees. Least width of color of underparts 24 per cent of greatest width of color of upper parts in each of two males and 19 to 30 per cent in three females. Black tip of tail longer than hind foot and averaging 40 (39-42) per cent of length of tail-vertebrae.

Skull and teeth.--Male (based on type specimen and adult no. 24132): See measurements and plates 27-29. As described in Mustela frenata macrura except that: Weight, 4.5 (4.2 and 4.8); basilar length, 44.6 (44.0-45.3); zygomatic breadth more than distance between condylar foramen and M1 or than between anterior palatine foramen and anterior margin of tympanic bulla; breadth of rostrum more or less than (approximately equal to) length of tympanic bulla; height of tympanic bulla less than distance from its anterior margin to foramen ovale; length of tympanic bulla less than length of rostrum; anterior margin of masseteric fossa posterior to m2 by length of that tooth.

Female (based on nos. 24134 to 24136): See measurements. As described in Mustela frenata macrura except that: Weight, 1.7 (1.5-1.9) grams; basilar length, 36.5 (35.3-38.1); zygomatic breadth less than distance between anterior palatine foramen and anterior margin of tympanic bulla; least width of palate more or less than (approximately equal to) outside length of P4; length of tympanic bulla less than length of rostrum.

The skull of the female averages 62 per cent lighter than that of the male.

The skull of the male is generally large and heavy as are the teeth. Comparison with macrura is made in the account of that subspecies. From males of affinis those of helleri differ in: skull shorter; breadth of rostrum and interorbital breadth actually and relatively greater.

Remarks.--The five specimens examined of this subspecies were taken by Edmund Heller for the Field Museum of Natural History in 1922 and 1923. It is to honor his contributions to mammalogy that the subspecies is named helleri. No. 24135 is the specimen carried as a pet for some time by Mr. and Mrs. Heller and of which Mrs. Heller (1924:481) has given an account.

This subspecies is insufficiently known, especially as to geographic range; probably it occupies a considerable range in the Tropical Life-zone along the eastern base of the Andes. The three females, two from Ambo and one from Huanuco, come from a much higher altitude than do the two males and the climate is said to be arid at Ambo and Huanuco. The skulls of the females are 62 per cent lighter and correspondingly smaller in measurements, than those of males. This difference is more than that found in any other South American weasel and it may be that the females are of a subspecies other than helleri.

The type specimen has a broad skull with major proportions strikingly like those of Mustela stolzmanni. Possibly the similar climatic conditions under which the two live have left their impress in similar fashion in this part of each of the two species. The teeth, tympanic bullae, and certain other parts of the skull are, however, so differently proportioned as to show that the skulls represent two species. The referred male has a much longer skull than the type specimen and the relative proportions of breadth and depth of the two skulls differ widely. Judging from large series of weasels examined from localities outside the range of M. f. helleri, the two skulls probably represent almost the maximum of individual variation occurring in one subspecies.

The dark color is as might be expected since helleri inhabits the humid Tropical Zone.

None of the five skulls shows signs of having had the frontal sinuses infested by parasites.

Specimens examined.--Total number, 5, all in the Field Museum of Natural History.

=Perú=: 3500 ft., Hacienda Buena Vista, Río Chinchao, 1; 3000 ft., Hacienda San Antonio, Río Chinchao, 1; Huanuco, 1; Ambo, 2.

=Mustela frenata agilis= Tschudi

Long-tailed Weasel

Plates 27, 28, 29, 39 and 40

Mustela agilis Tschudi, Fauna Peruana, p. 110, 1844; Gray, Proc. Zoöl. Soc. London, 1865:113, 1865; Taczanowski, Proc. Zoöl. Soc. London, 1874:311, 1874; Taczanowski, Proc. Zoöl. Soc. London, 1881:648, 1881; Allen, Bull. Amer. Mus. Nat. Hist., 35:104; April 28, 1916; Thomas, Proc. U. S. Nat. Mus., 58-224, 1920.

Mustela macrura, Allen, Bull. Amer. Mus. Nat. Hist., 35:103, April 28, 1916.

Mustela frenata agilis, Hall, Carnegie Instit. Washington Publ. 473:110, November 20, 1936; Hall, Physis, 16:176, 1939.

Type.--No type specimen, or type locality more restricted than cold, barren highlands of the Cordillera [referring to Perú] designated.

Range.--High, barren Cordillera of Perú (see Tschudi, orig. descr.); as here restricted, Temperate Life-zone and higher in western Andes and intermountain valleys of Perú. See figure 29 on page 221.

Characters for ready recognition.--Differs from Mustela frenata macrura by lighter color (Chocolate, tone 2 rather than 3, pl. 343, Oberthür and Dauthenay) of upper parts; length of upper tooth-rows, in females, less than 13; inside length of P4 more than 4.6; from M. f. aureoventris by smaller teeth (maximum size just given for agilis); from M. f. boliviensis by lighter color, upper parts being Chocolate, tone 2, pl. 343, rather than tone 4 or darker of Carbon Brown, pl. 342 (Oberthür and Dauthenay).

Description.--Size.--Male: The stuffed skin of an adult, from Lima, measures: Total length, 460; length of tail, 125; length of hind foot, 45.7. A skin alone from Huarochirí has a body, as now stuffed, 277 mm. long. The tail is missing and the bones of the hind feet have been removed.

Female: The mounted specimen, no. 565, Mus. Polonais d'Hist. Nat., yields measurements, taken by me, as follows: Total length, 250; length of tail, 75; length of hind foot, 32.5. The female, no. 21147, from Macate, measures, 300, 102, 34.