CICHLID.E. 459 



CICHLIDJE. 



Mouth protractile, the maxillaries excluded from the oral border. Lower pharyngeal 

 bones more or less completely united, with median suture *. A single nostril on each 

 side. No suborbital lamina supporting the globe of the eye. Gill-membranes free 

 from isthmus ; gills four, a slit behind the fourth. Pectoral fin with the pterygials 

 longer than broad, more or less regularly hourglass-shaped. Ventral fins thoracic, 

 with one spine and five soft rays. Dorsal and anal fins with strong, pungent spines. 

 Vertebrae with transverse processes from the third ; ribs most frequently sessile or sub- 

 sessile. Air-bladder present. 



Fresh- or brackish-water Fishes, some carnivorous, others chiefly herbivorous, inhabit- 

 ing Central and South America, Africa (including Madagascar), Syria, and India and 

 Ceylon. These Fishes have often been distinguished as " Chromides" a name which 

 properly pertains to their marine allies the Pomacentridoe. 



This is one of the largest and most interesting families of the African fresh waters. 

 A few years ago only about twenty species were known from Africa; we now 

 distinguish something like two hundred and ten species from that part of the world, 

 referred to about thirty-five genera. Most of the genera are based on the dentition, 

 which shows most extraordinary modifications, especially in Lake Tanganyika, the 

 fish-fauna of which consists chiefly of members of this family. 



The habits of these fishes are also highly interesting, many sheltering their eggs and 

 young in the mouth and pharynx. This parental care, which was formerly believed to 

 devolve on the male, appears to be invariably undertaken by the female, at least in the 

 African members of the family. 



Some years ago I pointed outf that the distinction of genera according to the 

 dentition, whether the teeth are conical or bi- or tricuspid, was not without presenting 

 some difficulties, some species showing bi- or tricuspid teeth when young and unicuspid 

 teeth when adult. These difficulties have further increased as our knowledge has 

 progressed, and have been brought to a climax by the enormous collection of Cichlids 

 made by Mr. Degen in Lake Victoria in 1905. The study of this collection has been 

 a bewildering one to me, specimens evidently of the same species showing every 

 possible grade between the two extreme types of dentition according to age and even 

 in individuals of the same size. It is evident that the shape of the teeth is often a very 



* Cf. PI. XCIV. figs. b-d. 



t Poiss. Bass. Congo, p. 393.— See also Pellegrin, Mem. Soc. Zool. France, xvi. 1904, p. 87. 



3 h 2 



