PETROCHEOMIS. 269 



of scaly part not greater than diameter of eye. Gill-rakers short, 

 20 to 28 on lower part of anterior arch. Dorsal XVI-XV1I 11-13 ; 

 spines strong, subequal from the sixth or eighth, |- to ^ length of head ; 

 longest soft rays § to f length of head. Anal III 9-10 ; third spine 

 a little shorter than longest dorsal. Pectoral longer than head, 

 extending a little beyond origin of anal. Ventral reaching vent or 

 origin of anal. Caudal truncate, slightly emarginate. Caudal peduncle 

 as long as deep or a little deeper than long. Scales not denticulate, 

 32-33 J7J20! lateral lines gfjg-. Olive above, silvery beneath; a more 

 or less distinct dark opercular spot ; vertical fins with dark and light 

 spots, or dorsal with dark oblique streaks. 



Total length 300 millim. 



Lake Taganyika. 



1-2. Types. Ujiji. E. Coode Hore, Esq. (C). 



3. Ad. Kilambo. Prof. J. E. S. Moore (C). 



4. Ad. Niamkolo. Dr. W. A. Ounnington (0.). 



5. Ad. Kitulu. „ 



6. Skel. Albertville. Cnpt. Hecq (C). 

 7-9. Yg. Mouth of Lobozi R. Dr. L. Stappers (C). 



The very young, about 30 millim. long, are very difficult to distinguish 

 from the young of Tilapia nilotica. They have likewise an ocellar 

 black spot on the anterior part of the soft dorsal. 



2. PETROCHROMIS ANDERSONIL 



Bouleng. Ann. & Mag. N. H. (7) viii. 1901, p. 13 ; Pellegr. Mem. Soc. Zool. 



Prance, xvi. 1904, p. 351 ; Bouleng. Fish. Nile, p. 535, pi. xcvi. (1907). 



Depth of body 2 to 2\ times in total length, length of head 3 times. 

 Head not quite twice as long as broad ; snout 1§ times as long as eye, 

 which is 4| to 5 times in length of head and 2 to 2 J times in inter- 

 orbital width ; mouth with thick lips, extending to between nostril and 

 eye ; 3 series of scales on the cheek, depth of scaly part equal to or 

 greater than diameter of eye. Gill-rakers short, 25 on lower part 

 of anterior arch. Dorsal XVI-XV1I 13; spines very strong, increasing 

 in length to the last, which measures about \ length of head ; longest 

 soft rays a little longer or a little shorter than head. Anal III 9-10; 

 third spine shorter than last dorsal. Pectoral much longer than head, 

 reaching beyond origin of anal. Ventral reaching anal. Caudal 

 truncate. Caudal peduncle slightly deeper than long. Scales not 

 denticulate, 32-34 j^ ; lateral lines rrzja- Olive above, the scales 



