TILAPIA. 



177 



3 times. Head 1| to 2 times as long as broad ; snout with straight or 

 convex upper profile, a little broader than long, f to f postocular part 

 of head ; eye 3 (young) to 4J times in length of head, 1 (yoang) to If 

 times in interorbital width, equal to or less than preeorbital depth ; 

 mouth rather small, f to f width of head, extending a little beyond 

 vertical of nostril ; teeth in 3 (young) to 6 series, 50 to 74 in outer series 

 of upper jaw ; 2 series of scales on the cheek, width of scaly part less 

 than diameter of eye. Gill-rakers short, 15 to 18 on lower part of 

 anterior arch. Dorsal XV-XVI 10-12; spines subequal from the 

 sixth, or last longest, f to -| length of head ; longest soft rays f to J 



Fig. 113. 



Tilapia macroceplui la . 

 Lagos, f. 



length of head. Anal III 7-9 ; third spine | length of head. Pectoral 

 1 to \\ times length of head, extending to vertical of origin of anal or 

 a little beyond. Ventral reaching vent or anal, or not so far. Caudal 

 truncate or feebly emarginate. Caudal peduncle deeper than long. 

 Scales cycloid, 27-30 ^zg^^ lateral lines J-J:J^. Brown above, 

 yellow or white beneath ; a black opercular spot ; chin and throat or 

 lower half of head often black, or spotted or rnarblcd with black ; dorsal 

 and caudal sometimes with round light spots ; anal grey or black ; ventrals 



