CHEYS1CHTHYS. 315 



with 6 rays, inserted behind the vertical of the dorsal fin. Fuur 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 prrecaudal and 24 to 27 caudal vertebra?. 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 1^ 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 interneural 



shield ; maxillary barbel a little longer 



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

 Occipital process in contact with interneural 



shield ; muxillary barbel g length of head ; 



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



II. Dorsal 1-1 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 3| 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 J f times as long as broad ; 



snout pointed, as long as broad ; 

 width of mouth 3^ times in length 

 of head ; anal with 9 branched 

 rays 3. C. acutirpslns, 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 ; 



