INTRODUCTION. 



The number of species of Fish described or noticed in the following Part of the 

 Zoology of the Beagle, amount to 137. It is right to observe that, judging from 

 Mr. Darwin's manuscript notes, relating to what he obtained in this department, 

 this is probably not more than half the entire number which he collected. 

 Unfortunately a large portion of the valuable collection sent home by him arrived 

 in this country in too bad condition for examination, and was necessarily 

 rejected. 



The localities visited by Mr. Darwin, and at every one of which more or fewer 

 species of fish were obtained, were the Cape Verde Islands, — the coast of 

 Brazil, including the mouth of the Plata, together with several inland rivers and 

 streams in that district, — the coasts of Patagonia, and the Santa Cruz river, — 

 Tierra del Fuego and the Falkland Islands, — the Archipelago of Chiloe, — the 

 coasts of Chile and Peru,— the Galapagos Archipelago, — Tahiti, — New Zealand, 

 King George's Sound in Australia, — and, lastly, the Keeling Islands in the 

 Indian Ocean. The great bulk of the species, however, are from the coasts, east 

 and west, of South America. 



The particular locality assigned to each species respectively in the following 

 work may be relied upon as correct ; pains having been taken by Mr. Darwin to 

 affix a small ticket of tin, with a number stamped upon it, to each specimen, and 

 to enter a note immediately in the manuscript catalogue, having the same number 

 attached. In only three or four instances these tickets were found wanting, 

 on the arrival of the collection in this country. 



A considerable portion of the species examined and described are new 

 to science, especially of those collected in South America, and the adjoining 

 Islands and Archipelagos. The new ones are supposed to amount to seventy-five 

 at least, constituting more than half the entire number ; and amongst these are 

 apparently seven new genera. 



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