468 TUBE-B LADDERED GROUP. 



African Loaches, — Family Kneriid^:. 



Two small loach-like fishes from the fresh waters of Tropical Africa, one of 

 which (Kneria congolensis) is figured in the annexed illustration, alone represent a 

 family distinguished from the preceding by the absence of teeth on the pharyngeal 

 bones, and by the elongated air-bladder being undivided, barbels being wanting. 

 While the figured species is from the west coast, the other (K. spehei) inhabits 

 Central Africa. 



The Characinoid Fishes,— Family Erythrinila:. 



As an example of a very extensive family of fresh-water fishes, confined to 

 Tropical America and Africa south of the Sahara, we select an American form 

 known as the piraya (Serrasalmo piraya), since in our limited space it is quite 

 impossible to deal with any of the others. It may be mentioned, in the first place, 



angola LOACH (nat. size). 



that these fishes are commonly known as the Characinidce, but as there is no 

 such genus as Characinus, it is obvious that this term cannot stand, and we have 

 accordingly adopted another. According to Professor Cope's arrangement, these 

 fishes belong to the same sectional group as the carp tribe, from which they may 

 be distinguished by the brain-case not being produced between the orbits, and 

 likewise by the number of upper pharyngeal bones varying from four to one 

 instead of being always two ; a further point of difference occurring in the 

 structure of the upper jaw, which is formed in front by the premaxillse, and at 

 the sides by the maxillae. Like the carps, the body is scaled and the head naked ; 

 but barbels are invariably wanting, and the jaws may be either toothless, or 

 furnished with a dentition of a very powerful type. In most cases there is a 

 small fatty fin behind the dorsal ; the air-bladder is always transversely divided 

 into halves, and there are no false gills. Unfortunately, there are no fossil forms 

 to aid in the explanation of the peculiar geographical distribution of the family, 

 which is very similar to that of the chromids ; but there can be little doubt that 

 the ancestral types originally inhabited the great land-mass of the Northern 

 Hemisphere, from whence they migrated southwards to their present isolated 



