Seven species occur in the Mediterranean region, all of which seem able to live in briny springs or pools, the water of which contains a much greater percentage of salts than sea-water, as the brine-springs near the Dead Sea or in the Sahara. They are as little affected by the high temperature of some of these springs (91°), for instance of that at Sidi Ohkbar in the Sahara. Like other fishes living in limited localities or concealing themselves in mud, Cyprinodonts lose sometimes their ventral fins; such specimens have been described as Tellia. The species of the New World are less known than those of the Old, but not less numerous.
Allied to Cyprinodon are Fitzroyia from Monte Video, and Characodon from Central America.
Haplochilus.—Snout flat, both jaws being much depressed, and armed with a narrow band of villiform teeth. Body oblong, depressed anteriorly, compressed posteriorly. Dorsal fin short, commencing behind the origin of the anal, which is more or less elongate.
Twenty species from the East Indies, tropical Africa, and temperate and tropical America.
Fundulus.—Cleft of the mouth of moderate width, developed laterally and horizontally. Snout of moderate length. Teeth in a narrow band, those of the outer series being largest, conical. Scales of moderate size. Dorsal fin commencing before or opposite the origin of the anal. Sexes not differentiated.
“Killifish,” abundant in the New World, where about twenty species have been found; F. heteroclitus, majalis, diaphanus, being common on the Atlantic coast of the United States; from the Old World two species only are known, viz. F. hispanicus from Spain, and F. orthonotus from the east coast of Africa. Allied to Fundulus are the South American Limnurgus, Lucania, Rivulus, and Cynolebias.
Orestias.—Ventral fins none. Cleft of the mouth of moderate width, directed upwards, with the lower jaw prominent, and with the upper protractile. Both jaws with a narrow band Of small conical teeth. Scales rather small or of moderate size, those on the head and upper part of the trunk frequently enlarged, plate-like, and granulated. Dorsal and anal fins moderately developed, opposite to each other. Sexes not differentiated by modification of the anal fin. The gill-membranes of both sides are united for a short distance, and not attached to the isthmus.
Inhabitants of Lake Titicaca and other elevated sheets of water on the Cordilleras of Peru and Bolivia, between the 14th and 19th degrees of latitude, at an elevation of 13,000 and 14,000 feet above the level of the sea. Singularly, the fishes of this outlying genus attain to a greater size than any other members of this family, being about eight inches long and comparatively bulky. They are considered a delicacy. Six species.
Jenynsia.—Cleft of the mouth small, developed laterally and horizontally; snout not produced. Both jaws with a series of tricuspid teeth of moderate size. Scales of moderate size. The origin of the anal fin is, in both sexes, behind that of the dorsal, although the anal of the male is modified into an intromittent organ, in which scarcely any of the rays remain distinct.
One species from Maldonado.