198 BULLETIN 144, UNITED STATES KATIONAL MUSEUM 



Vespenis iwlythrix Fitzingek, Sitzungsber. Akad. Wissensch. Wien, vol. 62, pt. 1, 

 p. 143, 1870. 



2ryctop1iylax nubilus Fitzingek, Sitzungsber. Akad. Wissensch. Wien, vol. 62, 

 pt. 1, p. 501, 1870. 



Myotis ruber Thomas, Ann. and Mag. Nat. Hist., ser. 7, vol. 10, p. 493, Decem- 

 ber, 1902. — Trouessakt, Catal. Mamm. viv. foss., suppl., p. 94, 1904. 



Myotis polythrix Trouessabt, Catal. Mamm. viv. foss., suppl., p. 94, 1904. 



Type locality. — Paraguay, probably near Asuncion, 



Type specimen. — None specified; the name is based on Azara's 

 " Chauve-souris onzieme, ou Chauve-souris cannelle." 



Distribution. — The range can not at present be accurately defined 

 It probably includes, however, southern and eastern Brazil, all of 

 Paraguay, northeastern Argentina, and the adjacent part of Peru. 



Diagnosis. — Like Myotis cMloensis but skull of adult normally 

 ynth. a conspicuous sagittal crest, and color usually reddish. Dis- 

 tinguishable from M. nigricans in the red phase by larger general 

 size, more robust teeth, and the normal presence of a sagittal crest. 



Extti^ial form. — The general external features, except as they are 

 modified by the animal's larger size, do not differ appreciably from 

 those of Myotis chilo'ensis and M. nigricans. The foot, however, is 

 proportionally as well as actually larger than is usual in either of the 

 better known species, the ratio of its length to that of tibia aver- 

 aging 54.1 in five specimens from Paragua}'. Calcar, as in M. chilo- 

 'ensis and M. nigricans, with a low but usually obvious keel. Ear as 

 long, relatively to muzzle, as in M. chilo'ensis, extending when laid 

 forward about 2 mm. beyond nostril. 



Fur and color. — The pelage in botR quality and distribution is 

 essentially as in Myotis nigricans. The hairs on the upper part of 

 the back are longest, about 6 mm. ; they lack conspicuous burnished 

 tips. 



There are, as in Myotis nig^ricans, two well-defined color phases, 

 rufous and brown, but, contrary to the conditions prevailing in the 

 smaller animal, it is the rufous phase which appears to be dominant. 

 In rufous pelage the entire dorsal surface to the roots of the hairs 

 is a bright " ochraceous tawny" (Ridgway, 1912), darkening on the 

 muzzle and on the chin to maroon or " russet," the tips of the hairs 

 without evident gloss. The under side of the body is a peculiar tint 

 of brownish yellow, close to "yellow ocher" (Ridgway), well shown 

 in D'Orbign}'^ and Gervais's figure; the bases of the hairs are darker, 

 nearly " Prout's brown." In the brown phase, upper parts " Prout's 

 brown," darkening at bases of hairs to " mummy brown," the tips of 

 the hairs with a slight gloss ; underparts essentially similar to back, 

 but the color so lightened as to suggest a dirty buff, darker on chin 

 and throat, paler posteriorly. 



