APPENDIX C. 
265 
branchial arch. Ventral fins inserted behind the origin of the 
dorsal^ which is nearer to the end of the snout than to the root 
of the caudal. Basal half of the caudal fin covered with small 
scales. There are from fifteen to sixteen abdominal scutes behind 
the base of the ventral fins. Operculum with irregular radiating 
striae descending towards the suboperculum. A large blackish 
blotch in the scapulary region^ sometimes followed by a series of 
four to six similar blotches. 
The shad^ which enters the Nile from the Mediterranean in the 
months of December and January^ is identical with the British 
Twaite-shad ; it has been described by Hasselquist as Clupea alosa; 
and Geoffrey St. Hilaire has given to it a distinct name, Clupea 
nilotica (^‘^Descr. Eg./^ p. 286, pi. 10, fig. 1.) 
OSTEOGLOSSIDjE. 
Heterotis, 
Body rather elongate, compressed, covered with large hard scales; 
head compressed, scaleless, bony ; abdomen rounded ; cleft of the 
mouth rather small, with the jaws subequal ; barbels none. A 
single series of small teeth in the jaws ; pterygoids and hyoid with 
a patch of small conical teeth ; none on the vomer or palatine 
bones. Gill membranes separate, with eight branchiostegals; the 
fourth branehial arch with a spiral accessoi'y organ. Air-bladder 
cellular. Dorsal fin long, opposite to the anal fin, close to the anal 
fin, without spines. Ventral fins far behind the pectorals. 
