320 



SILUEID.E. 



3J times. Head moderately depressed, 1^ to IJ times as long as broad, 

 its upper surface more or less rugose, the rugosities usually showing 

 under the thin skin ; occipital process narrow, extending to the small 

 interneural shield ; snout broadly rounded ; eye large, transversely oval, 

 its diameter once (young) to once and | in length of snout, 3 to 4J times 

 in length of head, IJ to 2 times in interocular width ; mouth inferior, its 

 width equal to or a little greater than interocular width ; prsemaxillary 

 band of teeth straight, 2J to 8J times as long as broad ; vomero-pterygoid 



Fig:. ^55. 



Chrysichthys avrriius. 

 Lower Nile (F. N.). 



teeth forming a narrow band narrowly interrupted in the middle, some- 

 times reduced to the vomerine part. Nasal barbel \ to f diameter of 

 eye; maxillary barbel f to nearly once length of head; mandibular 

 barbels shorter, inner about f or | length of outer. Gill-rakers rather 

 short. 10-12 on lower part of anterior arch. Dorsal I 6, IJ to 1\ 

 times as distant from root of caudal as from end of snout ; spine strong, 

 feebly serrated behind, f to | length of head ; first soft ray usually more 

 or less produced, sometimes much longer than head. Adipose fin as long 

 as or longer than base of rayed dorsal, usually shorter than its distance 

 from the latter. Anal 11-13, 6 or 7 (rarely 8) branched. Pectoral 

 shorter than head, not reaching ventral, with a strong spine, with 

 strong serrne on the inner side. Caudal deeply forked, the lobes acutely 

 pointed, upper often produced into a short filament. Caudal peduncle 

 1^ to If times as long as deep. Buffish grey above, silvery white 

 beneath ; an ill-defined dark transverse band behind the head and 

 another in front of the dorsal fin. 



