26 BULLETIN 117, UNITED STATES NATIONAL MUSEUM. 



spoke eloquently of the brevity of the watershed. June and July are said to be the 

 really dry months, when continuous sunshine is the rule. At midday the heat is 

 often intense, but the nights are seldom imcomfortable or hot. Malaria is rare at this 

 particular spot, but this is owing to the absence of mosquitoes, due to the good drain- 

 age of the land. From Yuvini you look out upon a wide valley bounded at some 

 distance by gently rounded hills, the whole landscape forest covered \vithout a cliff 

 or rock showing. 



Heller Expedition, September 7-13; 18-20; 28,1915; 46 specimens 

 of 33 species. 



Rio Comherciato (altitude 1,800-2,000 feet, liumid Tropical Zone). — 

 The Rio Comberciato enters the Urubamba from the northwest some 

 70 miles west by north of Santa Ana. This was the second of Heller's 

 two stations in the humid Tropical Zone. The collections from this 

 point and the Rio Cosireni (the second tropical station) represent 

 only a small portion of the existing fauna, but are sufficient to show 

 the zonal affinities of the region, Mr. Heller's notes follow: 



Parallelling the Cosireni River in a general way, but lying a few leagues farther 

 north is the Comberciato River which enters the Urubamba at its great bend. The 

 Comberciato has twice the volume of the Cosireni and is much less rapid. The valley 

 through which this stream flows is much deeper and narrower, however, than that of 

 its neighbor, but the river is a series of broad, quiet expanses separated by low, short 

 rapids free of projecting bowlders. The forest covers the whole landscape without 

 any interruptions due to barren rock surfaces or other causes. The hillsides are soil 

 covered like the valley floor. 



The lower course of the river where the Yuvini road drops down into the valley, 

 has an altitude of 1,800 feet and this level is maintained for several leagues as we 

 ascend the river. Our highest point on the river was a station called Arroj^o at which 

 point a wire cable has been erected by the rubber gatherers for passing their cargoes 

 of rubber. This point is about 4 leagues up the river at the termination of the road 

 and has an altitude of 2,000 feet. Climatically the valley is much warmer than the 

 Yuvini District, owing to its lesser elevation. 



At nights there is a continuation of the heat, but little less than in the shade at 

 midday. The river playas or beaches are extensive and wide, the older ones being 

 covered by a growth of tall, spiny bamboo and the newer beaches by glistening white 

 pebbles. A few species of trees occur here which are not found at Yuvini, but the 

 country in general is quite identical to the Cosireni Valley. 



Heller Expedition, September 4-6; 13-15; 21-25, 1915. 

 LIFE ZONES OF THE URUBAMBA VALLEY. 



My reconnaissance in the Urubamba Valley and subsequent study 

 of our collections from it have had for their object the determination 

 of the life zones of this section of the Andes and comparison of them 

 with those which we have found to exist in Colombia. 



Field experience in the last-named country enabled me to make 

 this comparison in part in the field, while Pleller's excellent descrip- 

 tions of the district visited by him, which I saw only at a distance 

 or did not reach at all, in connection with fairly representative col- 

 lections, permit me to present at least a provisional report on the 

 subject under consideration. -. 



