(veers 
XXUI ACANTHOPTERYGIL 671 
present ; palate toothless ; lower pharyngeal bones more or less 
completely united, with median suture. Vertebrae with para- 
pophyses from the third ; ribs most frequently sessile or subsessile. 
A single nostril on each side. Gill-membranes free from isthmus ; 
5 or 6 branchiostegal rays; gills 4, a slit behind the fourth; 
pseudobranchiae absent. Dorsal fin, with numerous spines; anal 
with 3 spines or more. Ventral fins with 1 spine and 5 soft rays. 
Fresh or brackish-water fishes, variable in form and dentition, 
some carnivorous, others chiefly herbivorous. In some American 
forms (Cichla) the males and females differ during the spawning 
season, the male developing a hump on the top of the head, which 
Fic. 410.— Tilapia dardennii, from Lake Tanganyika. § nat. size. 
disappears afterwards. The eggs and young are cared for by the 
parents ; either the male or the female, according to the species, 
sheltering them in the mouth or pharynx.’ These fishes, often 
designated as “Chromides,” a name which properly pertains to 
members of the following family, inhabit Africa, Madagascar, 
Syria, India and Ceylon, and Central and South America, from 
Texas to Uruguay. About 45 genera are distinguished, based 
mostly on the number of anal spines and the dentition, which for 
variety of types is comparable to that of the Characinidae. Of 
these 45 genera, 30 are African. 150 species are known from 
Africa (with Syria and Madagascar), 140 from America, and 3 
from India and Ceylon. Principal genera—African : Lampro- 
logus, Hemichromis, Paratilapia, NXenotilapia, Tropheus, Tilapia, 
1 It has recently been ascertained, on a large number of specimens, that in the 
African species the female alone performs the buccal nursing duties. 
2 Cf. Monograph by J. Pellegrin (Paris, 1904). 
