2i8 Field Museum of Natural History — ZoGlogy, Vol. X. 



and others. The collection at hand, therefore, is the first large and 

 general one made in the fresh waters of the Isthmus. 



The present survey was made after much work had been done on the 

 Canal and natural conditions had been considerably disturbed, but yet 

 before the water was turned into the Canal and before the species from 

 the two slopes were allowed to intermingle. The natiu-al conditions 

 had at the time of our visits been most disturbed in the Rio Grande on 

 the Pacific slope of the Canal Zone. This stream had been thoroughly 

 cut to pieces and in view of this fact it seemed important, in order to 

 obtain a comprehensive knowledge of the fishes of the Canal Zone, to 

 extend the survey to other Pacific slope streams. In this connection it 

 is an interesting fact that several species, namely, Pimelodella chagrest, 

 Plecostomus plecosiomus, Astyanax fasciatus, Brycon argenteus, Curimatus 

 magdalenos, Thoracocharax niaculatus, Priapichthys tridentiger and 

 Microeleotris panamensis gen. et sp. nov., taken in streams both east and 

 west of the Rio Grande were not found in it, the presimiption being 

 that they once occvirred there but that they had disappeared on accoimt 

 of the unfavorable conditions created by the construction of Canal. 



Two small preliminary papers containing the descriptions of new 

 species have already been published in the Zoological Series of Field 

 Museum of Natural History (Vol. X, 1912 and 1913, pp. 67 and 68, and 

 pp. 77 to 91). In the present and final report we have endeavored to 

 give concise descriptions of all the species known to occur in the fresh 

 waters of Panama, along with keys which we believe will afford ready 

 means of identification. We have avoided technical terms as far as 

 possible and hope that the work may prove of use in the high schools 

 of the Canal Zone, and in other institutions of learning in Panama, as 

 well as to ichthyologists. A complete report on the marine species is 

 in the course of preparation and will be offered later. 



The senior author, on account of ill health, was obliged to with- 

 draw from the work during the course of its preparation. His untimely 

 death occurred on July 6, 1914, thus delaying greatly the completion 

 of the report. In the fall of 191 5 Prof. C. H. Eigenmann of Indiana 

 University kindly offered the use of his library, collections from Colom- 

 bia and other South American coimtries, and his laboratory at the 

 University for the further study of this collection. Advantage was 

 taken of this opporttmity, the specimens were shipped to Bloomington, 

 and the study of them was there completed by the jimior author, who is 

 much indebted to Prof. Eigenmann for many valuable suggestions and 

 for aid in classifying difficult forms. Without the Colombian collection 

 for comparison, many forms, the relationship of which is now definitely 

 established, would have remained tmknown. 



