INTRODUCTION. 



This fourth volume, which concludes the ' Catalogue of the Fresh-water 

 Fishes of Africa,' contains the last families of Acanthopterygii and 

 the Opisthomi and Plectognathi (135 species, 1390 specimens), an 

 Appendix dealing with the additions to the literature and the 

 collection since the publication of the preceding volumes (issued in 

 1909, 1911, and 1915, respectively), and Indexes to the whole work. 



The collection, the arrangement of which is now completed, is 

 certainly the largest ever brought together and described from the 

 fresh waters of any part of the world, comprising as it does over 

 15,000 specimens, or more than one-half of the total number of Fishes 

 in the British Museum at the conclusion of Dr. Giinther's Catalogue in 

 1870. At that date — a land-mark in the history of systematic Ichthy- 

 ology — very little was known of the fresh-water fishes of Africa, and 

 even ten years later, in his ' Study of Fishes,' Dr. Gunther assessed the 

 number of species then known at 255 only, intentionally omitting a 

 few forms such as occur also in the sea (the Anguillidce and Mugilidce, 

 for instance). In a list compiled by me ten years ago, the number of 

 species was estimated at 974. 1425 are described in the present work. 



In addition to the 15,000 specimens in the Museum, it has been my 

 privilege to examine a nearly equal number, principally from the Nile 

 Survey, the Congo (Tervueren), Genoa, Paris, S. African, and Luxemburg- 

 Museums, and the collections made by the late Dr. W. J. Ansorge, 

 who, up to the time of his death two years ago, had been most 

 energetic in exploring various rivers of West Africa, from Portuguese 

 Guinea to Angola, and who, within the last fifteen years, on his own 

 initiative, has done more than any other collector for the increase of 

 our knowledge of African Fishes. Next in importance, and in addition 

 to those mentioned in the ' Fishes of the Nile ' and in the Introduction 



