476 



Annals of the South African Museum. 



Ectodus, are of considerable interest owing to their mode of spawning 

 and the nursing habits of the parent fish. In the Tilapia, for instance, 

 it lias been observed that in some species the ova are deposited in a 

 small hollow or nest made in the bed of a pond or stream, and after 

 fertilisation by the nude who is very determined in attacking and 

 driving off any strange fish are taken into the mouth of the female 

 and carried in the buccal cavity until hatched. Mr. Schoeller, in 

 some observations made at Alexandria (Egypt), noticed that the 

 young fry after hatching took refuge in the mother's mouth imme- 

 diately any alarm or danger appeared. 



Formerly these nursing duties were believed to devolve upon the 

 male, but careful examinations by Dr. Boulenger and others show that 

 it is always the female that undertakes them, and that she apparently 

 goes without food during the ten days or so that elapse whilst the eggs 

 are hatching in her mouth. 



Synopsis of the South African Genera described. 



Dorsal and anal fins without scaly sheath at the base. 



A. Outer teeth bi- or tricuspid, rarely conical, with- 



out canines in front, not swollen at the 



base. 

 Teeth forming narrow or moderately broad 



bands, the outer bicuspid, rarely conical ; 



dorsal with 11-19 spines, anal with 3 or 4 . 

 Teeth forming very broad bands, all tricuspid ; 



dorsal with 16-20 spines, anal with 3 . 



B. Outer teeth biciispid in some individuals, conical 



in others (forms connecting Tilazria and 

 Paralilapia) ; dorsal with 13-19 spines, 

 anal with 3-6 ...... 



C. Outer teeth conical in the adult, sometimes bi- 



cuspid in the young, with or without 

 curved canines. 



Anal with 3 spines (exceptionally 4). 



Outer teeth, if closely set, not strongly in- 

 curved. 



Two lateral lines ; ventrals with the outer 

 rays longest. 



Outer mandibular teeth not pointing out- 

 wards. 



Two or more series of teeth in each jaw ; no 

 strong papillose pad in front of the gill- 

 arches ; dorsal with 10-18 spines, anal with 

 6-14 soft rays Paratilapia, Blkr. 



Tilapia, A. Smith. 

 Petrochromis, Blgr. 



Haplnchromis, PfeiY. 



