364 FISHES. 



First Family — PoLYPTEEiciE. 



Scales ganoid ; fins without fulcra. A series of dorsal 

 spines, to each of which an articulated finlet is attached ; anal 

 placed close to the caudal fin, the vent being near the end of the 

 tail. Abdominal portion of the vertebral column much longer 

 than the caudal. 



PoLTPTERus. — Teeth rasp-like, in broad bands in the jaws, 

 on the vomer and palatine bones ; jaws with an outer series of 

 closely-set, larger, pointed teeth. Caudal fin surrounding the 

 extremity of the vertebral column ; ventral fins well developed. 

 A spiracle on each side of the parietal, covered with an osseous 

 plate. A single large gular plate. Air-bladder double, commu- 

 nicating with the ventral wall of the pharynx. 



Fig. 144. — Polypterus bichir. 



This Ganoid is confined to tropical Africa, occurring in 

 abundance in the rivers of the west coast and in the Upper 

 Nile ; but it has not been found in the river-systems belonging 

 to the Indian Ocean. It is scarce in the Middle and Lower 

 Nile, and the specimens found below the Cataracts have 

 been carried down, from southern latitudes, and do not pro- 

 pagate their species in that part of the river. There is only 

 one species known, Polypterus bichir ("Bichir" being its 

 vernacular name in Egypt), which varies in the number of 

 the dorsal finlets, the lowest being eight, the highest eighteen. 

 It attains to a length of four feet. Nothing is known of its 

 mode of life, and observations thereon are very desirable. 



Calamoichthys. — Distinguished from Polypterus by its greatly 

 elongate form, and the absence of ventral fins. 



C. caldbaricus, a dwarf form from Old Calabar. 



