GYMNARCIIIDiE. 225 



Fam. 11. GYMNARCHID^. 



Body and tail scaly, head scaleless; barbels none. 

 The margm of the upper 'jaw is formed in the middle 

 by the intermaxillaries, which, in mature individuals, 

 coalesce into a single bone, and laterally by the max- 

 illaries. Sub- and interoperculum present, small • 

 on each side of the parietal bone a cavity leading into 

 the interior of the skull, and covered with a thin bony 

 lamella. Dorsal fin extending nearly o\eY the entire 

 length of the back ; tail tapering, without fin ; anal 

 and ventral fins absent. Vent nearly in the middle 

 of the length of the fish. A series of pores along the 

 base of the dorsal fin. Pseudobranchiae none ; gill- 

 opening reduced to a slit on each side. Two cseca 

 pylorica behind the stomach. 



Rivers of Tropical Africa. 

 One genus only. 



1. GYMNARCHUS. 

 Gymnarchus, Cuv. R^gtie Anim. 



Each jaw with a single series of incisors; no teeth on the palate. 

 Air-bladder cellular, very extensible, perhaps with the functions of 

 a lung. 



1. Gymnarchus niloticus. 



Jerfar, Rifand, Voy. Effuptc, pi. 1.38b. fig. 1 (bad). 



Gymnarchus niloticus, Cuv. Rh/ne Auim. ; J^rdl, Ahhandl. Bayr. Akad, 

 Wiss. 1847, p. 209 (osteol.) • Meckel, Denkschr. ylkad. Wtss. Wien, 

 18.54, vi. p. 11, taf. l-2T^II;/rtl, Denkschr. Akad. Wiss. Wien, 185G, 

 xii. p. 1, c. tab. (anat. and osteol.). 



D. 203-208. 



The length of the head is contained four times and one-third in 

 that of the dorsal fin, and once and two-thirds in its distance from 

 the vent. Seven teeth on each side of the intermaxillary. Pectoral 

 fin rather shorter than the snout. 



Nile ; rivers of West Africa. 



a. Adult. Upper Nile. From Mr. J. Pethcrick's Collection. 

 b-c. From four to five feet long : stuffed. West Africa. Purchased 

 of Mr. Dalton. 



d. Fine half-grown specimen. West Africa. Purchased of Mr. Dalton. 



e, f. Young, II inches long. West Africa. 

 (/. Adult. Purchased of Mr. Frank. 



h. Adult: stuff'cd. Purchased of M. Par/.udaki. 

 ?'. Skull of specimen b. 



VOL. VI. 



