Fam. 8. Lepidosteidae.—Body elongate, with a relatively short caudal region. Tail semi-heterocercal. Scales rhombic, thick, ganoin-coated and articulated, not vertically elongated on the sides of the body. Dorsal and anal fins short and remote from the pelvic fins. Median fins with fulcra. Both the upper and lower jaws more or less elongated, forming a broad and depressed or a long tapering beak, near the anterior end of which the nostrils are placed. Eyes small. Vertebral centra well ossified, opisthocoelous and fused with the neural arches. The metapterygoid bones have a secondary articulation with the skull.[[590]] Maxillae segmented into numerous pieces. Jugular plates absent. Branchiostegal rays reduced to three on each side. Teeth numerous, slender, and of unequal size. In the larger teeth the dentine is intricately folded. Pyloric caeca branched and compacted together into a gland-like mass. Air-bladder cellular, but its blood is not derived from a posterior aortic arch.
The only known genus is Lepidosteus, the existing species of which frequent the fresh waters of North America.[[591]] The common or Long-nosed Gar-Pike (L. osseus), remarkable for its long and slender beak, is generally abundant in the rivers and lakes of the United States from Vermont to the Rio Grande, and it may reach a length of five feet. The "Short-nosed Gar" (L. platystomus, Günther) has a much shorter and broader beak, and a similar distribution (Fig. 299). The "Great" or "Alligator Gar" (L. viridis, Günther) has a more southerly habitat, frequenting the rivers of the Southern States, Northern Mexico, and Cuba. It is by far the largest species, sometimes reaching a length of 8 to 10 feet.
Fig. 299.—Short-nosed Gar Pike (Lepidosteus platystomus.) × ⅛. (From Bashford Dean, after Goode.)
Lepidosteus is a voracious Fish, preying upon smaller Fishes, and, except in the breeding season, it frequents the deeper parts of the rivers or lakes. The Fish is constantly in the habit of rising to the surface and emitting bubbles of gas, either through the mouth or by the branchial clefts, and it is probable that this gas is air which has been previously swallowed at the surface and passed into the air-bladder. About May Lepidosteus resorts in large numbers to shallower water, where the temperature is higher, for the purpose of spawning, each female being attended by from one to four males.[[592]] During brief recurring periods of excitement, accompanied by convulsive lashing movements, the eggs and sperm are emitted. The eggs are extremely sticky, and adhere tenaciously to the rocks and stones on which they are deposited. In a few days the embryos hatch out, and at this stage the larva has a huge mouth surmounted by a terminal preoral disc, fringed with a row of marginal wart-like suckers (Fig. 300). The yolk sac is so large as greatly to hamper the movements of the larva; hence, by means of its suckers, the young Lepidosteus attaches itself to surrounding objects, and remains almost entirely motionless for some little time after hatching. Later, about a fortnight after escaping from the egg, the yolk becomes completely absorbed, the suckers degenerate and eventually disappear, and the larva, freed from its load of nutritive reserve, assumes a more active life. After the absorption of the yolk the larvae of Mosquitos appears to form the exclusive diet of the young Lepidosteus for some time, but very soon young Fishes are readily devoured.[[593]]
Fig. 300.—Larval Lepidosteus osseus, 11 mm. long. a, Anus; a.f, c.f, d.f, developing anal, caudal, and dorsal fins; m, mouth; ol, olfactory organ; op, operculum; pt.f, pectoral fin; s, sucker. (From Balfour and N. Parker.)
Lepidosteus seems to have been abundant in Europe during the Eocene and Miocene periods, but became extinct before the Pliocene. In North America, also, the genus dates from the Eocene, and still survives.
Order IV. Teleostei.
[For the account of this Order, see pp. [541] f.]