INTRODUCTORY. 3 



not been examined before, and many of the forms are 

 new. 



A most valuable collection was made by His Majesty 

 Dom Pedro II. in the Rio Grande do Sul, which has not 

 been studied before, and many of the forms are new or 

 otherwise interesting. 



The collection of the Thayer expedition is by far the 

 richest collection of fresh water fishes ever made in 

 South America. It is scarcely necessary to enumerate 

 here the advantages which would have accrued to Ameri- 

 can students and to this museum had this enormous 

 collection been studied shortly after it was made. No 

 systematic attempt has before been made to examine all 

 the specimens of any of the families of fresh water fishes 

 collected during this expedition. The result has been 

 that most of the new forms having been rediscovered by 

 other collectors the types of numerous species are now 

 scattered through various museums in America and 

 Europe which would be found in the Museum of Com- 

 parative Zoology if this collection had been studied at 

 once. Even those specimens which have hitherto served 

 as the types of new species are not so labeled, rendering 

 very difficult the identification of the rest at this time. 



A large collection was made during the Hassler expe- 

 dition around South America; specimens were secured 

 at Santiago, Callao and Panama. Part of this material 

 had not been studied and has yielded new forms. 



A valuable collection was made by Mr. Alexander 

 Agassiz and Mr. Samuel Garman in Lake Titicaca. 

 Many small collections came from private travellers. 

 The names of the collectors are mentioned with the de- 

 scriptions of the specimens. 



We are indebted to Mr. Alexander Agassiz, the di- 

 rector of the Museum of Comparative Zoology, for the 



