In the second division of cartilaginous fishes, or sturgeons, the gills are free, as in the ordinary fishes. In the sturgeon the gill-openings are a single, very wide orifice, with an operculum, but without radiating membrane. They are fishes of great size, living in the sea, but ascending the larger rivers in the spawning season. Our space only permits us to notice the Chimæra and Sturgeon.
The naturalists Clusius and Aldrovandus compared the fish, to which they gave the name of Chimæra arctica, to the chimæra, a monster of mythological antiquity, which is represented with the body of a goat, the head of a lion, the tail of a dragon, and a gaping throat which vomited flames. The strange form of this fish, the manner in which it moves, the different parts of its muzzle, its mode of showing its teeth, its ape-like contortions and grimaces, its long tail, which acts with such rapidity,—reminding one not a little of a reptile,—are well calculated to strike the imagination. At a later period mediæval naturalists were contented to see in it a fish with a lion's head, and as the lion was then regarded as the king of animals, so the chimæra became the Herring king.
Fig. 355. The Arctic chimæra.
The king of the herrings (Fig. 355) is from five to six feet in length, of a general silvery colour, spotted with brown. It inhabits the North Sea, living on molluscs and crustaceans; occasionally, as if to justify the title which has been given it, levying heavy contributions upon the herrings. Another species, C. antarctica, is found in the southern hemisphere, which greatly resembles, in its conformation and habits, the northern species. In both the end of the muzzle terminates in a cartilaginous appendage, which projects forward, curving afterwards over the mouth. This extension assimilates to a crest.
The sturgeons (Acipenser) are among the largest fishes known. On this account, as well as from their exterior conformation, they approach the Squalidæ. Their muscles, however, are less firmly knit, their flesh more delicate, and their muscular strength consequently infinitely smaller. Neither is their mouth armed with so many rows of teeth. Moreover, they are less voracious, and their habits are not at all ferocious.
The sturgeons are sea-fishes which periodically ascend the larger rivers. Several species are known in Europe. They abound in the Black Sea and Sea of Azof, but they are chiefly known as frequenting the Volga and the Danube. The enormous consumption of caviare in Russia leads to a deadly pursuit of the common sturgeon in all the great European rivers, and this species is in a fair way of disappearing altogether.
Fig. 356. The Common Sturgeon (Acipenser sturio).