Fig. 409.—Ditrema temminckii, from Japan. × ⅓. (After Jordan.)
Small or moderate-sized fishes inhabiting California and Japan, mostly marine, one species, however, inhabiting fresh waters, whilst another descends to a great depth. They feed mostly on crustaceans, but one genus (Abcona) is herbivorous. The name "Surf-Fishes," by which they are generally known, refers to the fact that most species are found in the surf along sandy beaches. All are viviparous in the strictest sense of the term, the young remaining for a long time closely packed in a sac-like enlargement of the oviduct analogous to a uterus; they are of relatively large size at birth, and quite similar in form to the parent, whilst at an earlier period they differ in having the vertical fins much more elevated. Twenty-four species are known.[[716]] Principal genera: Hysterocarpus, Abcona, Cymatogaster, Embiotoca, Ditrema.
Fam. 33. Cichlidae.—No subocular shelf; entopterygoid present; palate toothless; lower pharyngeal bones more or less completely united, with median suture. Vertebrae with parapophyses 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.
Fig. 410.—Tilapia dardennii, from Lake Tanganyika. ⅓ nat. size.
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 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.[[717]] 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.[[718]] Principal genera—African: Lamprologus, Hemichromis, Paratilapia, Xenotilapia, Tropheus, Tilapia, Asprotilapia, Eretmodus, Plecodus, Pseudetroplus. American: Acara, Heros, Hygrogonus, Cichla, Crenicichla, Chaetobranchus, Geophagus, Symphysodon, Pterophyllum. Indian: Etroplus.
No part of the world surpasses Lake Tanganyika in variety of generic and specific types of Cichlidae, the fish-fauna of this great lake being in great majority made up of members of this family.
Fig. 411.—Distribution of the Cichlidae.
Priscacara, from the Eocene of North America, is the only extinct genus which can be referred to this family.