360 Natural History Bulletin. 



specimens of a small fresh-water Prosobranchiate Mollusc, 

 probably Potamopyrgus, and several small fishes, etc. Only- 

 one trip was made to the Los Sabalos, namely on the ist of 

 March, 1893, the journey to its mouth being made by steamer, 

 and beyond that by canoe. The return trip to Castillo was 

 made by canoe on the San Juan River. 



The collections along both the La Juana and Los Sabalos 

 were made along the banks in close proximity to the water, 

 neither time nor circumstances permitting an exploration of 

 the deep forests beyond. 



Climatic Conditions and their Effect. 



In the vicinity of Castillo the dry season begins much later 

 than it does at Ometepe, nor is it as sharply defined. It usu- 

 ally begins about the end of January, but this year it was de- 

 layed so that the end of February passed before it fairly set in. 

 This gave the party a slight taste of the rainy season at its 

 close, and suggested the difficulties which the naturalist would 

 encounter when this season is at its height. 



Of the 41 days, from February 12th to March 23rd, which 

 were spent in Castillo and vicinity, 21 were more or less rainy, 

 4 were cloudy, and 16 were clear. Of the 21 rainy days 7 

 were quite stormy, while only light showers fell during the 

 remaining fourteen days. Of the 16 clear days, 11 occurred 

 in March, which was decidedly drier than February. The 

 dews and morning fogs were heavy during this period, and 

 the atmosphere was very humid. 



The North-east Trade-wind was felt daily. It usually com- 

 menced to blow at about 10 o'clock a.m., and continued until 

 evening, the nights and mornings being calm. 



The range of temperature was about the same as on Ome- 

 tepe. The days were very warm, and the nights quite cool, 

 particularly toward morning when heavy blankets were al- 

 ways acceptable. 



No diminution in the freshness and vigor of the vegetation 

 was observable up to the time of leaving Castillo, though no 



