REPORT ON ROTATORIA FROM PANMIA WITH DESCRIP- 

 TIONS OF NEW SPECIES. 



By Harry K. Harring, 



Custodian of Rotatoria, United States National Museum. 



INTRODUCTION. 



Tliis report is based on a large number of collections made by Dr. 

 C. Dwight Marsh during the months of January and February, 1912. 

 That no complete picture can be given of the rotatorian fauna of the 

 Isthmus of Panama is self-evident, as all the collections were made 

 during the dry season and but very little material was narcotized, so 

 that the contractile forms were with few exceptions unrecognizable. 

 However, the loricate species were abundant and furnished interesting 

 material. The Isthmus is not a specially favorable collecting ground 

 for aquatic invertebrates, as there are no lakes and but few permanent 

 pools; nevertheless it will be seen from the list of Rotatoria that when 

 suitable conditions are present the fauna is both abundant and varied. 



The following extract from Marsh ^ \vill give some idea of the envi- 

 ronment: 



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 6 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 the 

 collections on the southern elope within the limits of the Canal Zone were made either 

 in water which had been artificially impoimded 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 30 miles. Two considerable rivers come into the Canal Zone 

 from this slope, the Rio Chagres and Rio Trinidad. On the lower reaches of these 

 rivers, and this is especially true of the Trinidad, are extensive swamps. The Chagres 

 is a swift-flowing stream, sometimes torrential in character, and does not furnish a 

 suitable environment for any extensive development of plankton organisms. The 

 swamps form a suitable environment for plankton, but, connected together as they are, 

 would not lead one to expect any great variety. 



Gatun Lake will eventually be a large body of water with a surface of 164 square 

 miles and a depth of 47 feet. At the time the collections were made the lake was very 



1 Marsh, C. Dwight, Report on fresh-water Copepoda from Panama with descriptions of new species. 

 Smiths. Misc. Coll., vol. 61, No. .3, 1913. 



Proceedings U. S. National Museum, Vol. 47— No. 2062. 



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