xxi MALACOPTERYGII 551 



authors. Ninety-three species are known from the fresh waters 

 of Africa north of the Tropic of Capricorn, and may be referred 

 to two sub-families and ten genera l : 



(i.) MORMYRINAE, with teeth on the parasphenoid and tongue, 

 with ventral, anal, and caudal fins, and a simple air-bladder ; 

 vertebrae 37 to 64 ; peculiar (Gemmingerian) linear bones, with- 

 out known homologues, along each side of the tail, above and 

 beneath the electric organ ; scapular foramen in the scapula, or 

 between the scapula and the coracoid. Mormyrops, Petrocephalus, 

 Isichthys, Marcusenius. Stomatorliinus, Myomyrv.s, Gnathonemus, 

 Genyomyrus, Mormyrus. 



(ii.) GYMXARCHINAE, without teeth on the parasphenoid and 

 tongue, without ventral, anal, or caudal fins, and with a cellular 

 air-bladder; vertebrae about 120; Gemmingerian bones absent; 

 scapular foramen in the coracoid. Gymnarchus. 



Fossil Mormyrids are unknown. 



Venerated by the ancient Egyptians, the Mormyrs of the Nile 

 are frequently represented on hieroglyphics and mural paintings 

 as well as in bronze models. Very little is known of the habits 

 of these Fishes. Prof. G. Fritsch, of Berlin, during his stay in 

 Egypt for the purpose of experimenting on electric Fishes, observed 

 that they perish very rapidly when removed from the river, and 

 he had the greatest difficulty in keeping some alive in an aquarium 

 for two or three days. The species with comparatively large 

 mouths (Mormyrops, Gymnarchus} feed principally on fishes and 

 crustaceans, the others on tiny animals and vegetable and more 

 or less decomposed matter. Delhez, on the Congo, found that 

 many are attracted to the borders of the river in the neighbour- 

 hood of human dwellings, where they feed on the refuse thrown 

 into the water. It is probable that the species with a rostrum 

 use it to procure small prey hidden between stones or buried 

 in the mud, and that the fleshy mental appendage with which 

 many are provided is a tactile organ compensating the imperfec- 

 tion of the vision in the search for food. A small Mormyrid from 

 the Congo (Stomatorhinus microps} has the eyes so much reduced 

 and the skin so feebly pigmented as to convey the impression of 

 a cave Fish. Until quite recently, absolutely nothing was known 



1 For a general account of the Fishes of this family, cf. Boulenger, P.Z.S. 1898, 

 p. 775, and Poissons du Bassin du Congo, p. 49 (1901), where a bibliographical index 

 to the principal anatomical and physiological publications will be found. 



