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Show 278 PISCES. their reduction to mere vestiges concealed under the skin, while their functions are fulfilled by bones analogous to the ]Jalatines and even sometimes by the vomer. The gelatinous substanc:, which in other fishes fills the intervals of the vertebrre and only communicates with them by a small hole, forms a Jon; cord in several of the Chondropte~ygii, which traverses the bodies of almost all the vertebrre, Without scarcely vary· ing in diameter. This series is divided into two orders-the Chondroptery~i whose branchire are free, like those of ordinary fishes, and those in which they are fixed, that is to say, attached to the skin by their external edge in such a manner that the water can only escape from their intervals through holes on the surface. l , ORDER I. STURIONES, OR CHONDROPTERYGII BRANCHIIS LIBERIS. Or Chondropterygii, with free branchire, which are still closely allied to the ordinary fishes in their gills, which have but a single wide opening, and are fu·rnished with an operculum, but without rays in the membrane. This order comprises but two genera. AciPENSER, Lin.(l) The general form of the Sturgeon' is similar to that of the Shark, but the body is more or less covered with bony plates in longitudi· nal rows; the exterior portion of the head is also well mailed; .the mouth, placed under the snout, is small and edentated; the palatme, soldered to the maxillaries, converts them into the upper jaw, .and vestiges of the intermaxillaries are found in the thickness of the hps. This mouth, placed on a pedicle that has three articulations, is more (1) .B.cipenser is the ancient name; Siu7'io, whence Sturgerm, is modern, and i~ probably the German name Stoet· latinized. CHONDROPTERYGII DRANCHIIS LIBERIS. 279 protractile than that of the Shark. The eyes and nostrils are on the side of the head, and cirri are inserted under the snout. The labyrinth is perfectly formed in the cranial bone, but there is no vestige of an external ear. A hole perforated behind the temple is a mere spiracle, which leads to the branchire. The dorsal is behind the ventrals, and the anal under it. The caudal surrounds the extremity of the spine and has a salient lobe beneath, shorter, however, than its principal point. Internally, we already find the spinal valve of the intestine and the united pancreas of the Selachii, but there is, moreover, a very large natatory bladder, which communicates with the resophagus by a wide hole. The Sturgeon ascends certain rivers in great numbers, and is the object of important fisheries; the flesh of most species is agreeable, their ova are converted into caviar, and their natatory bladder into isinglass. Western Europe produces .fl. sturio, L.; Bl., 88. (The Common Sturgeon.) Six or seven feet long; snout pointed; plates strong and spinous, arranged in five rows; the flesh resembling veal. The rivers which empty into the Black and Caspian seas, in addition to the sturio, produce three other species, and perhaps more.(l) .11. Ruthenus, L.; .fl. pygmreus, Pall., Bl., 89. (The Sterlet.) Seldom more than two feet in length; plates of the lateral rows more numerous and carinated, those of the belly flat. It is considered a delicious fish, and its caviar is reserved for the Russian court. There is reason to believe that it is the Elops and the .B.cipenser, so highly celebrated among the ancients.(2) .11. helops, Pall.; .11. stellatus, Bl. Schn.; Marsili., Dan. IV, :x.ii, 2; the Scherg of the Germans; Sevreja of the Russians. Four feet in length, and has a longer and more slender snout, and rougher plates than the others. This species is excessively numerous, but is less valued than the Sturgeon. .11. huso, L.; Bl., 129; the Hausen, &c. (The Great Sturgeon.) Blunter plates and a shorter snout and cirri than those of the Common Sturgeon; the skin also is smoother. It is frequently (1) The various species of the Sturgeon are not yet well determined, and even Pallas, who knew more of them than any one else, does not give them sufficiently distinct comparative characters; he does not agree either with Kramer, Guldenstedt, or Lechepin. The figures of Marsigli, on the other hand, are too coarse. We expect better ones from the learned Austrian naturalists, to whom the Danube offers abundance of these fishes. (2) See my note on Pliny, Lemaire's Ed. vol. II, p. 74. \ |