PARENTAL CARF. AINtONG PRESH-WATER FISHES. 



479 



and the extent of the dorsal and anal fins. The osteological and 

 cerebral variation is also great and the differences between the 

 ordinary forms (^lormyrines) and the genus Petrocephalus are 

 so many as to have led to the isolation of the last as a distinct 

 subfamily type. Representatives of the Mormyrines occurring in 

 the Nile were reverenced by the ancient Egyptians, and various myths 

 were connected with them. 



There is a great range of size in the family, and even rather 

 closely related species may represent extremes. For example, the 

 largest of the family {Mormyrops deliciosus) 

 sometimes becomes five feet long, while a con- 

 gener of the same fauna {Mormyrops parvus) 

 may be sexually mature when less than five inches 

 long. 



The food of the Mormyrids naturally is deter- 

 mined by the means for obtaining it. Those with 

 a relatively large mouth are able to secure fishes 

 and moderate-sized crustaceans ; those with mouths 

 of reduced size are limited mainly to small crus- 

 taceans and worms and the larv?p of insects, supplemented by decay- 

 ing animal and vegetable matter and some live plants. Bovdenger 

 thinks that the species with prolonged snouts make use of them to 

 })ry out animalcules which have found refuge between stones or 

 which have buried themselves in the mud, and that the fleshy ap- 

 pendage at the tip of the lower jaw is a tactile organ by means of 

 Avhich they are assisted in finding their food. Some, indeed, seem 



Fig. 59.— Petrocephalus. 



Via. GO. — Moniiijnis u.ii)rliijnvlm>i. Aftei- Ueoft'i-uy Saint Ililairo. 



to prefer decomposing matter, and among such is the Monnyrops, 

 delic'iosHs, which Delhez declared affected jjutrifying animals in the 

 midst of the water weeds where they occur in large numbers; 

 especially did they congregate in the neighborhood of encampn.ients, 

 where refuse matter of all kinds was dumped into the water. l>nl that 

 very species exercised a rather wide range of choice, for Peters and 

 Boulenger found in stomachs the remains of fishes and crustaceans. 



The longest, if not the best known, of the Mormyrids is the Cas- 

 chive {Mormyrus caschice) of the Nile, which, however, is by no 



