PETROCHEOMIS. 



535 



7. PETKOCHROMIS. 



Boulenger, Trans. Zool. Soc. xv. 1898, p. 20, and Poiss. Bass. Congo, p. 179 (1901) ; 

 Pellegrin, Mem. Soc. Zool. France, xvi. 1904, p. 350. 



Barely separable from Tllapia, differing only in the broader bands of teeth in the 

 jaws, the teeth being all very slender with expanded tricuspid crowns bent inwards. 



Two species from Lake Tanganyika, one from Lake Nyassa, and one from Lake 

 Albert. 



rig. 38. 



Dentition of: Petrochromis cuidersonii. 



1. PETROCHROMIS ANDERSONIL 



(Plate XCVI.) 



Boulenger, Ann. & Mag. 2ST. H. (7) viii. 1901, p. 13 ; Pellegrin, t. c. p. 351. 



Depth of body twice and one-fifth in the total length, length of head three 

 times. Snont once and two-thirds the diameter of the eye, which is contained five 

 times in the length of the head and twice and one-fonrth in the interorbital width ; 

 month with thick lips, extending to between the nostril and the eye ; teeth extremely 

 numerous, all tricuspid ; three series of scales on the cheek ; large scales on the 

 opercle. Gill-rakers short, 25 on lower part of anterior arch. Dorsal fin with 

 16 spines and 13 soft rays ; spines very strong, increasing in length to the last, which 



