HETEROBRANCHUS. 



273 



1. HETEROBRANCHUS BIDOllSALIS. 



I. Geoffr. Descr. Egypte, Poiss. p. 305, pi. xvi. figs. 2 & 5, & pi. xvii. figs. 8 & 9 

 (1827) ; Giintli. Petherick's Trav. ii. p. 220 (1869) ; Bouleng. Fish. Nile, 

 p. 300, pi. liv. fig. 1 (1907), and Proc. Zool. Soc. 1907, p. 1095. 



Heterobranchus geoffroyi, Ouv. & Val. Hist. Poiss. xv. p. 392 (1840). 



Heterobranchus senegalensis, Cuv. & Val. t. c. p. 397 ; Steind. Sitzb. Ak. Wien, lx. 

 1869, p. 980. 



Heterobranchus intermedins, Giinth. Cat. Fish. v. p. 22 (1864), and 1. c. 



Depth of body 6 to 9 times in total length, length of head 2-f to Z\ 

 times. Head very strongly depressed, 1^ to 1| times as long as broad, 

 its upper surface coarsely granulate in the adult; occipital process 

 pointed, sometimes very obtusely ; frontal fontanelle knife-shaped, 3 to 

 4 times as long as broad, 3 to 5 times in length of head ; occipital 

 fontanelle small, in advance of occipital process ; eye 3 (young) to 6| 

 times in length of snout, 6 to 10J times in interorbital width ; width of 

 mouth a little less than interorbital width ; band of prgemaxillary teeth 

 about 5 times as long as broad ; vomerine teeth also villiform, forming a 



Fig. 226. 



Heterobranchus bidorsalis. 

 White Nile (F. N.). J-. 



crescentic band which is 1^ to 1^ times as broad as the prsemaxillary 

 band and may have a small central posterior process ; nasal barbel -f to 

 once length of head ; maxillary barbel ■§• to If times length of head, 

 extending to extremity of pectoral or between this point and root of 

 ventral ; outer mandibular barbel 1-j^j to 1^ times as long as inner, 

 which measures 1 to 1^ times length of head. Gill-rakers rather 

 short, 20 to 30 on anterior arch. Dorsal 38-45, its distance from 

 occipital process to to ^ length of head ; adipose dorsal f to § as long 

 as, as deep as or lower than, and commencing immediately behind, 

 rayed dorsal, extending to base of caudal. Anal 50—57, extending to 

 base of caudal. Pectoral f to \ length of head, the spine smooth 



VOL. II. T 



