134 ^ YEAR OF COSTA RICAN NATURAL HISTORY 



dipterous larvae (Chironomids allied to Tanypus and CuH- 

 coides), a weevil {Anchonus coarctatus) previously recorded 

 only from Cerro Zunil in Guatemala, and small planarian 

 worms (probably the young of Rhynchodemus bromelicola). 



The northern rim of crater III falls away on the north 

 side perfectly vertically, to a depth of one hundred and 

 fifty to two hundred feet, to a valley filled with luxuriant 

 vegetation. So sheer is the precipice and so narrow is the 

 rim that it is difficult to see how the wall has been retained 

 on this side. 



Crater G is one of the latest of these vents of Irazu. We 

 saw a slight quantity of steam or vapor issue from it. Its 

 walls are very steep and we did not risk a fall into it in order 

 to see the deepest part. Some sulphur coats part of its walls 

 and floor, as is the case with the north wall of crater II also. 

 Professor Pittier reported sulphur vapors issuing from G or 

 H in 1888, but both Dr. Sapper and Professor Tristan assert 

 that since that time no activity has been observed in any of 

 the craters. Our observation just mentioned, of steam or 

 vapor issuing from G, stands in contradiction to these 

 statements. 



The really active part of Irazu, in recent years, is on the 

 north slope of the mountain, at an elevation of about 9250 

 feet, outside of all the craters. In December, 1888, and 

 January, 1889, Professor Pittier found the entire slope in 

 activity with blue clouds of sulphurous smoke and hot water 

 flowing. Dr. Sapper, on February 28, 1889, found only a 

 few fumaroles but no hot water springs. This locality, 

 termed "boca nueva" or "volcancillo" by the Costa Ricans, 

 we did not visit. 



We returned to the tent level by climbing the trail through 

 the cinders on the inner (eastern) slope of the western rim 

 of daughter-crater III. This western rim seems to belong 

 to both daughter and mother-craters or else the western rim 



