32 MOKMYEID^. 



2. PETROCEPHALUS. 



Marcusen, Bull. Ac. St. Petersb. xii. 1854, p. 14 (part.) ; Gill, Proc. Ac. Philad. 1862, p. 443 ; 

 Boulenger, Proc. Zool. Soc. 1898, p. 787, and Poiss. Bass. Congo, p. 70 (1901). 



Teeth in the jaws bicuspid, forming a single complete or nearly complete series on 

 the entire edge of both jaws (10 to 24 in the upper jaw, 18 to 36 in the lower); 

 minute conical teeth on the parasphenoid and on the tongue ; mouth inferior, situated 

 below the eyes. Nostrils close together, close to the eye. Body short ; ventral fins 

 nearer the pectorals than the anal. Dorsal and anal fins not very unequal in length. 

 Vertebrae 42-44 (9-12 + 4-6 + 27-29). 



Ten species are known, four of which are represented in the Nile system. 



Synopsis of the Species, 



I. Anal fin originating in advance of dorsal. 



Dorsal 29-33 ; anal 31-37 ; diameter of eye less than interoeular width . 1. P. bane, Lacep. 



Dorsal 22-26 ; anal 30-35 ; diameter of eye less than interoeular width . 2. P. bovei, C. & V. 



Dorsal 25 ; anal 38-39 ; diameter of eye equal to interoeular width . . . 3. P. keatingii, Blgr. 



IT. First dorsal and anal rays in the same vertical. 

 Dorsal 19 ; anal 27 ; diameter of eye less than interoeular width .... 4. P. 



1. PETROCEPHALUS BANE. 

 (Plate VI. fig. 1.) 



Mormyrus bane, Lacepede, Hist. Poiss. v. p. 620 (1803) ; Cuvier & Valenciennes, Hist. Poiss. xix. 



p. 276 (1846) ; Giinther, Cat. Fish. vi. p. 220 (1866), and Petherick's Trav. ii. p. 254 (1869). 

 Mormyrus cyprinoides (non Linnaeus), I. Greoffroy, Descr. Egypte, Poiss. p. 277, pi. viii. figs. 3 & 4 



(1827). 

 Mormyrus dequesne, Cuvier & Valenciennes, t. c. p. 281. 

 Mormyrus joannisii, Cuvier & Valenciennes, t. c. p. 282. 

 Mormyrus ehrenbergii, Cuvier & Valenciennes, t. c. p. 283. 

 Petrocephalas bane, Marcusen, Bull. Ac. St. Petersb. xii. 1854, p. 14, and Mem. Ac. St. Petersb. (7) 



xiL 1864, no. 4, p. 146 ; Boulenger, Proc. Zool. Soc. 1898, p. 788. 

 P etrocephalus dequesne, Marcusen, Bull. p. 14. 

 P etrocephalus dejoannis, Marcusen, 1. c. 

 Petrocephalas ehrenbergii, Marcusen, 1. c. 



Body very strongly compressed, its depth twice and a half to three and one-third 

 times in the total length ; length of head three and three-fourths to four and a half 



