58 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



PhylloHs Thomas, P. Z. S., 1884, 449 (as a subgenus of Hesperomys). 

 Mils [PhylloHs) darwinii Waterhouse designated as type. 

 Phyllotis, on the one band, closely approaches Eliginodontia (see anfea, 

 p. 50), and on the other' is not very sharply separable from Reithrodon, 

 through such species as ''Phyllotis'' boliviaua and '' Reilhrodou'' pictus. 

 About 20 to 25 species and subspecies have thus far been assigned to the 

 group, which has about the same geographical range as Eliginodoiifia, 

 namely, from southern Patagonia northward over the plateau region east 

 of the Andes to northern Bolivia, and through the Andean region north 

 to Ecuador. The two Patagonian species here included were both de- 

 scribed by Waterhouse in 1837 ^^om specimens collected by Darwin, and 

 are both well represented in the Princeton University Expedition col- 

 lections. 



Phyllotis xanthopygus (Waterhouse). 



(Plates XIII, Fig. i, Skull ; XIV, Figs. 2 and 3, Teeth.) 



Mns [Phyllotis) xanthopygtis Waterhouse, P. Z. S., 1837 (N(5v. 21, 1837), 



28. Santa Cruz, Patagonia. 

 Mus xanthopygtis Waterhouse, Zool. Voyage Beagle, Mamm., 1839, 63, 



pi. xxii, animal, pi. xxxiv, fig. 16, teeth. 

 Hesperomys [Calouiys) xanthopygus Burmeister, Descript. phys. Rep. 



Argent, III, 1879, 225 (ex Waterhouse.) 

 Hesperomys [Phyllotis) xanthopygus Milne-Edwards, Mission Scient. du 

 Cap Horn, VI, Zool., Mamm., 1890, 20, pi. vi, fig. 2, animal. Santa 

 Cruz, Patagonia. 

 Phyllotis xanthopygus Trouessart, Cat. Mamm., ii, 1897, 534 (^^ Water- 

 house and Thomas). — Lahille*, Congr. Cien. Lat. Amer., Ill, 1899, 187. 

 Adult (November). — Pelage very soft and very long and full. Gen- 

 eral color above, from the eyes posteriorly, dull brown varied with black- 

 tipped hairs and faintly suffused with buff or pale fulvous, darkest over 

 the median area, the sides more buffy and less dark, passing into a strong 

 buff lateral line, indistinct above ; ventral surface whitish (under fur dark 

 plumbeous, scarcely showing at the surface), faintly washed in most speci- 

 mens with very pale buff, giving the general effect of soiled yellowish 

 white; whole front of head from a point midway between ears and eyes 

 gray, varied with black-tipped hairs ; hairs at base of tail rusty fulvous ; 

 ears large, dark brown, rather thinly furred ; upper surface of feet whitish, 

 palms and soles flesh-color ; tail about one half the total length, generally 



