218 Fretp Museum or Narurat History — Zoétocy, Vor. 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 natural 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 plecostomus, Astyanax fasciatus, Brycon argenteus, Curimatus 
magdalene, Thoracocharax maculatus, Priapichithys 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 presumption being 
that they once occurred there but that they had disappeared on account 
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 Zodlogical 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 1915 Prof. C. H. Eigenmann of Indiana 
University kindly offered the use of his library, collections from Colom- 
bia and other South American countries, and his laboratory at the 
University for the further study of this collection. Advantage was 
taken of this opportunity, the specimens were shipped to Bloomington, 
and the study of them was there completed by the junior 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 unknown. 
