VI IXTEODUCTION. 



Gray, Ayres, Day, Sauvage, and Pellegrin. In most cases when^ no 

 figures had been given, or when the figures were unsatisfactory, original 

 drawings have been prepared by Mr. J. Green and Mr. A. H Searle. 

 Whenever a figure is reproduced from a previous publication, the 

 source has been indicated. The initials A. M. C. refer to the quarto 

 plates of the ' Annales du Musee du Congo,' F. N. to those of the 

 ' Fishes of the Nile.' 



In making use of the descriptions and keys as drawn up in this work, 



it should be borne in mind that the fins are not included in the total 



length or greatest depth, whilst in the indication of the total length of 



the largest specimen examined, which follows the description of every 



species, the fish is measured from the end of the snout to the extremity 



of the middle rays of the caudal fin ; by depth of the caudal peduncle, 



?. e. the free part of the caudal part of the body between the bases 



of the dorsal or anal and caudal fins, is meant the least depth, whilst 



the length is that of the muscular part only, the root of the caudal 



rays being usually covered with scales. By length of the dorsal and 



anal fins is meant the basal length. The abbreviations used in the fin 



and scale formulse are too well known to all who work at fishes to need 



explanation here ; I will only observe that when both Roman and Arabic 



numerals are used to denote the number of dorsal or anal rays, the 



former refer to the simple or to the spinous rays, and the latter to the 



soft, branched rays, the last of which is usually cleft to the base, and 



that the interpolation of a comma between the numerals indicates 



discontinuity in the fins. 



G. A. BOULENGER. 



ZooLORiCAL Department, 

 2Mi Febntary, 1909. 



