X INTRODUCTION. 



species. They may not be new, or they may not be species at all, — but they 

 will be known; and any mistake which has been committed will be at once 

 rectified, — any new name which has been wrongly imposed, immediately degraded 

 to a synonym. 



Accordingly I have been careful in this respect; and I have in some in- 

 stances, given full descriptions, even of species which are certainly not new, but 

 which I did not find described by previous authors with all the detail that was 

 requisite for completely identifying them ; or, leaving out what they have noticed, 

 I have added such characters as they have omitted. My main object has been 

 to render all the species, whether rightly named or not, easily recognizable ; and, 

 however little the science may be advanced by what is brought forward, to make 

 that advance, so far as it goes, sure. 



The method of description, and the mode of computing the fin-ray formula, 

 will be found conformable to the plan adopted in the " Histoire des Poissons" of 

 Cuvier and Valenciennes ; a work which, in so many respects, must always 

 serve as a model to labourers in this department of zoology. 



The colours, in the great majority of instances, were, fortunately, noticed by 

 Mr. Darwin in the recent state. The nomenclature employed by him for the 

 purpose is that of Patrick Syme ; and he informs me, that a comparison was 

 always made with the book in hand, previous to the exact colour in any case 

 being noted. Where I have observed any markings left unnoticed by Mr. 

 Darwin, I have added them myself; and, in most instances, I have given the 

 general disposition of the colours as they appear in spirits, from the circumstance 

 of their being often so much altered by the liquor, and liable to mislead those, 

 who have only the opportunity of seeing them in preserved specimens. This is 

 what Cuvier and Valenciennes have frequently done in their work ; and from 

 them I have borrowed the practice. 



In a work of this nature, it has not been thought desirable to enter into any 

 discussion of the principles of scientific arrangement, or to effect any change in 

 systems already received ; its main object being the description of species. For 

 this reason, I have taken the groups almost exactly as they stand in the " Histoire 

 des Poissons" of Cuvier and Valenciennes, or in the " Regne Animal" of the 

 former : yet there is reason to believe that many parts of their system will be 

 found hereafter to require some modification, especially in regard to families and 

 genera which have for their distinctive character the presence or absence of 

 vomerine or palatine teeth. The small value which is to be attached to such 

 character is pointed out in some instances in the following work, and much 

 dwelt upon. 



