4 AOTUS 



in the East, to the Upper Amazon on the banks of the Cassiquiare River 

 near the headwaters of the Rio Negro, Brazil, and westward to £ga, 

 in Peru. A. roberti has only been obtained in the Sierra de Chapada, 

 Matto Grosso, Brazil ; and A. infulatus at Para. The only other 

 locality in the eastern part of the continent inhabited by a member of 

 this genus, is the right bank of the River Paraguay, northeastern part 

 of Argentina, where A. miriquouina is found. A. vociferans has 

 been procured on the Ucayali and Huallaga rivers, and at Tabatinga, 

 Upper Maranon, on the eastern border of Peru, and also in the 

 Tolima Mountains, south western Colombia. In the mountains just 

 named A. lanius was obtained. A. griseimembra has been found in 

 Santa Marta, and on the Rio Sinu Cerete, Bolivar, northern Colombia. 

 Two species inhabit Ecuador, A. gularis at the mouth of the 

 Rio Coca, Upper Rio Napo, and A. microdon at Micas. Peru, besides 

 A. trivirgata, has two other representatives of the genus, A. nigri- 

 ceps from Chanchamayo, and A. senex from Pozuzo, but the extent of 

 their range is not yet known, and this may be also said of most of the 

 other species. From the Province of Sara, Central Bolivia, A. bolivi- 

 ENSis comes. Three species remain whose habitats are doubtful or 

 unknown. First of these is A. rufipes mentioned above, received in 

 London alive from San Juan del Norta, Nicaragua. The type is 

 unique and its habitat uncertain, as it may have been brought to San 

 Juan from South America. The others are A. oseryi in the Paris 

 Museum, whose only habitat is given as "Haute Amazone, Perou," (I. 

 Geoff.) ; and A. spixi in the Collection of the same Institution, and 

 said to have come from "Amerique Meridionale." 



KEY TO THE SPECIES. 



A. Black lines on sides of head not going to the throat. 

 a. Black lines on head not going to the occiput. 



a.' Black lines from eyes encircling the white and 

 meeting on crown. 

 a." Apical half of hairs on tail black to the 

 roots. 

 a."' Black lines on head broad. 



a* Hairs on back red and black 



towards root A. infulatus. 



b.* Hairs on back slaty black 



towards root A. nigriceps. 



h."' Black lines on head narrow A. senex. 



