CHRYS1CHTHY8. 315 



with 6 rays, inserted behind the vertical of the dorsal fin. Four pairs 

 of barbels : nasal, maxillary, and two mandibulars. Nostrils widely 

 separated from each other. Eye supero-lateral, with free border. 

 Maxillary bone rather large, hidden in the lip but bordering the mouth ; 

 jaws with a band of villiform teeth ; a band of teeth on the vomer, often 

 extending also on the pterygoids. Gill-membranes free, deeply notched. 

 Air-bladder large, free. 



10 to 20 praecaudal and 24 to 27 caudal vertebrae. 8 to 10 branchio- 

 stegal rays. A more or less distinct foramen above the axil, leading to 

 the membrane of the air-bladder. 



Nile and Tropical Africa. 



Synopsis of the Species. 



I. Dorsal l-£ to 2 times as distant from root of caudal as from end of snout ; 



band of prsemaxillary teeth curved, 6 times as long as broad ; length of 

 head 4 to 4^ times in total length ; caudal deeply forked, longest rays at 

 least 3 times as long as median ; base of adipose fin not more than ^ its 

 distance from rayed dorsal. 

 Occipital process not reaching interne nral 



shield ; maxillary barbel a little longer 



than head ; anal with 10 blanched rays . 1. C. sianenna, Blgr., p. 317. 

 Occipital process in contact with interneural 



shield ; maxillary barbel § length of head ; 



anal with 8 branched rays 2. C. sharpii, Blgr., p. 318. 



II. Dorsal 11 to 1£ times as distant from root of caudal as from end of snout ; 



band of prsemaxillary teeth straight or feebly curved, 2£ to 4 times as long 



as broad ; length of head 3 to 3f times in total length ; maxillary barbel 



not longer than head. 



A. Base of adipose fin shorter than that of rayed dorsal, from which it is 



separated by a space equal to 2 to 4 times its length ; caudal deeply 



forked, longest rays at least 3 times as long as median : 12-20 gill-rakers 



on lower part of anterior arch. 



1. Head 1 § times as long as broad ; 



snout pointed, as long as broad ; 

 width of mouth 3} 2 times in length 

 of head ; anal \s ith 9 branched 

 lays 3. C. acutiroslris, Gthr., p. 310. 



2. Head 1J- to 1£ times as long as broad. 

 Snout rounded, broader than long ; width of 



mouth 2\ to 3 times in length of head ; 



