PREFACE. 



Dh. Gunther observes, — " This volume contains the Siluroid fishes, 

 and those families which, being provided with an adipose fin, were 

 formerly associated with the Salmonoids. Miiller proved them to 

 be distinct families, separating the Characinoids and Scopeloids : 

 however, natural as is the former of these families, very hetero- 

 geneous forms are included in the latter. The genus Salanx, which we 

 shall treat of in the sixth volume, is the type of a distinct family. 



" The publication of the present volume has been much delayed in 

 consequence of a thorough re-examination of the large family of 

 Siluroid fishes ; the manuscript was finished, when the Trustees of 

 the British Museum acquired the unique collection of Dr. Bleeker's 

 Siluroids, thus rendering necessary a revision of the descriptions and 

 of the systematic arrangement. 



" If we compare the number of species known at present with that 



contained in the corresponding parts of Cuvier and Valenciennes'a 



Histoire Naturelle des Poissons,' we find it nearly doubled, viz. : — 



Total number of species in Cuv. & Val 492 



Total number of species in this volume 1005 



Species apparently well characterized in Cuv. & Val 400 



Species apparently well characterized in this volume .... 849 



" More than 170 have been added from the Collection of the British 

 Museum, which again has been much enriched by numerous acquisi- 

 tions, of which the following are the more important : — 



" l.r The typical specimens of Siluroids described by Dr. P. Bleeker. 



" 2. The remainder of the typical specimens of Pharyngognaths, de- 

 scribed by the same author, and not contained in the fourth volume 

 of this work. 



" 3. A Collection of the Fishes of the Essequibo River, made by 

 H. Ehrhardt. 



