REPORT ON FRESH-WATER COPEPODA FROM PANAMA, 

 WITH DESCRIPTIONS OF NEW SPECIES * 



By C. DWIGHT MARSH 



of the u. s. department of agriculture 



(With Five Plates) 



PLANKTON COLLECTIONS OF THE SMITHSONIAN BIOLOGICAL 

 SURVEY OF THE PANAMA CANAL ZONE 



These collections were made by Meek and Hildebrand, in connec- 

 tion with their work on fishes in the seasons of 191 1 and 1912, by 

 Goldman in 191 2, and by Marsh who was present in Panama for 

 four weeks in 1912 for the express purpose of making" such collections. 

 Most of the collections were made within the limits of the Canal Zone. 

 A few collections were made in eastern Colombia, some on Rio Bayana 

 and its tributaries, some on the Chagres and Trinidad outside the 

 Zone and some in the neighborhood of Chorrera and of old Panama. 



The general character of the country is not especially favorable to' 

 the growth of plankton organisms either in variety or numbers. There 

 are no lakes in the Canal Zone and comparatively few permanent 

 pools. 



The continental divide is close to the southern shore of the isthmus. 

 From the summit of the divide to high tide on the Pacific side is only 

 about six miles. The slope consequently is very steep and whatever 

 water falls runs away almost immediately. During the season when 

 the collections were made there was practically no rain on this slope, 

 so that it was difficult to find any fresh water. Consequently nearly 

 all collections on the southern slope within the limits of the Canal 

 Zone were made either in water which had been artificially impounded, 

 or in the standing water in the deeper parts of streams that were 

 otherwise dry. 



The northern slope extends from the divide to the Atlantic, a 

 distance, in a straight line, of something over thirty miles. Two 

 considerable rivers come into the Canal Zone from this slope, the 

 Rio Chagres and the Rio Trinidad. On the lower reaches of these 



1 The present paper is the nineteenth dealing with the results of the Smithson- 

 ian Biological Survey of the Panama Canal Zone. 



Smithsonian Miscellaneous Collections, Vol. 61, No. 3 



1 



