248 PROCEEDINaS OF THE NATIONAL MUSEUM. vou. 58v 



64. MARMOSA IMPAVIDA Tschadi, 



Adult male, Torontoy, 8,000 feet (No. 194378). 



The examination of this specimen, with its really white mider- 

 surface, has made me revise the determination of our small Peruvian 

 Marmosae. This character had not previously been observed in any 

 Peruvian species, but now Mr. Heller's specimen corresponds sa 

 closely with Tschudi's description, both in this and other respects^, 

 that it should certainly be regarded as impavida. In consequence, 

 the specimens from Chanchamayo and Marcapata that I had pre- 

 viously called impavida, as also those from Yurimaguas, so named 

 by Mr. Osgood with laj connivance, need redetermination. On the- 

 whole it appears to me that they may suitably be called M. noctivaga 

 Tschudi, a form which I had wrongly assigned to M. cinerea, but 

 whose type I have since seen in Neuchatel and have taken a measure- 

 ment of its teeth, which closely correspond with those of the Chan- 

 chamayo examples. 



The skull and teeth of M. impamda are markedly smaller than 

 those of noctivaga, agreeing in fact very nearly with those of M. 

 quichua, the latter being distinguishable mainly by its cream-buffy 

 throat and chest and broadly slate-based belly hairs with buffy fawn 

 tips. 



Even on the white undersurface of Mr. Heller's specimen there is 

 an unsymmetrical area on the side of the chest where the hairs are 

 slaty gray at base, but this is obviously an individual variation. 



[MABMOSA QUICHUA Thomas.] 



[A specimen in the British Museum from Ocobamba, Cuzco. No. 

 98.11.6.18. Type. Collected by O. Garlepp.] 



65. PERAMYS PERUVIANUS Osgood. 



Two males from Ocobamba VaUey, 9,100 feet (Nos. 194379-80). 



These two specimens, caught in the same place on successive days,. 

 differ remarkably in color, but agree in so many essential characters 

 that they must, I think, belong to the same species. No. 194379 is 

 grayish above, anteriorily, while 194380 is more uniformly brown, 

 and very like P. adustus; but the former is very old, with worn 

 teeth, and the grayness is probably due to senility. Then also 194379 

 has the buffy abdominal patches described in the type, while, like 

 P. adustus, 194380 is without them. This again, however, may be 

 an age characteristic — a point which further material can alone 

 elucidate. 



The British Museum possesses no Per amy s from Peru, the two de- 

 teriorated examples described by Osgood being the only Peruvian 

 examples of the genus on record. 



