Fig. 276.—Botia rostrata. From Bengal.
This genus is more tropical than any of the preceding, and the majority of the species (eight in number) are finely coloured. The more elevated form of their body, and the imperfect ossification of the capsules of the air-bladder, the divisions of which are not side by side, but placed in the longitudinal axis of the body, indicate likewise that this genus is more adapted for still waters of the plains than for the currents of hill-streams.
Other genera from tropical India are Lepidocephalichthys, Acanthopsis, Oreonectes (hills near Hong-Kong), Paramisgurnus (Yan-tse-Kiang), Lepidocephalus, Acanthophthalmus, and Apua.
Fourth Family—Kneriidæ.
Body scaly, head naked. Margin of the upper jaw formed by the intermaxillaries. Dorsal and anal fins short, the former belonging to the abdominal portion of the vertebral column. Teeth none, either in the mouth or pharynx. Barbels none. Stomach siphonal; no pyloric appendages. Pseudobranchiæ none. Branchiostegals three; air-bladder long, not divided. Ovaries closed.
Small loach-like fishes from fresh waters of tropical Africa; two species only, Kneria angolensis and K. spekii, are known.
Fifth Family—Characinidæ.
Body covered with scales, head naked; barbels none. Margin of the upper jaw formed by the intermaxillaries in the middle and by the maxillaries laterally. Generally a small adipose fin behind the dorsal. Pyloric appendages more or less numerous; air-bladder transversely divided into two portions, and communicating with the organ of hearing by means of the auditory ossicles. Pseudobranchiæ none.
The fishes of this family are confined to the fresh waters of Africa, and especially of tropical America, where they replace the Cyprinoids, with which family, however, they have but little in common as far as their structural characteristics are concerned. Their co-existence in Africa with Cyprinoids proves only that that continent is nearer to the original centre, from which the distribution of Cyprinoids commenced than tropical America. The family includes herbivorous as well as strictly carnivorous forms; some are toothless, whilst others possess a most formidable dentition. The family contains so many diversified forms as to render a subdivision into groups necessary. They have not yet been obtained in fossiliferous strata.
I. Erythrinina.—Adipose fin absent.