330 PISCES. 



THE FIRST ORDER OF CHONDROPTERYGII,— 



CHONDROPTERYGII BRANCHIIS LIBERIS,— 



(Or, with free gills), have in their gills a single wide opening, and a gill-lid, like the Bony 



Fishes, but they have no gill-rays. There are two genera. 

 Accipenser, the Sturgeon. — General form like that of the Shark, but the body more or less covered 



with bony plates in longitudinal rows, and the head externally armed with the same. Their mouth, 



placed under the muzzle, is small and toothless ; and the palatal bones, soldered to the maxillaries, 



form the upper jaw, while 

 there are vestiges of the in- 

 termaxillaries in the thick 

 lips. Placed upon a pedicle 

 of three articulations, this 

 mouth is more protractile 



Fi ff 146.-THc S.ur.eon. ^ ^ q{ ^ g^ . 



the eyes and nostrils are on the sides of the head, and barbules are suspended from the muzzle; the 

 labyrinth within the cranial bones is perfect, but there is no external ear — the hole behind the temple 

 leading merely to the gills. The dorsal is behind the ventrals, and has the anal directly opposite to it; the 

 caudal surrounds the extremity of the spine, and terminates in the upper lobe of the tail, but an under 

 lobe gives the tail the appearance of being forked. Internally, we find the spiral intestinal valve, and 

 the single pancreas of the Shark family; and there is a very large air-bladder, which communicates 

 with the gullet by a large opening. Sturgeons ascend some rivers in vast numbers, and are the object 

 of valuable fisheries. The flesh of most is agreeable, their eggs or roes are made into caviar, and their 

 air-bladders furnish the finest isinglass. 



A. sturin, the Common Sturgeon, occasionally found in the west of Europe and on the British shores, is about 

 six feet Ion?, has a pointed muzzle, five rows of plates with strong spines, and its flesh is much esteemed, being 

 somewhat like veal. The rivers falling into the Black and Caspian Seas produce this and three other species, if not 

 more. A. ruthenus, the Sterlet, is seldom more than two feet long, with the plates on the lateral line numerous and 

 keeled, and those in the belly flat. It is considered delicious, and caviar made from it is reserved for the 

 Russian court. There is reason to believe that this is the Elops and Accipenser so much celebrated by the ancients. 

 A. stelatus, the seroregia of the Russians, and the scherg of the Germans, grows to the length of four feet, has the 

 plaits rougher and the snout more slender than the others. It is very numerous, but less esteemed than the 

 Common Sturgeon. A. huso, the Great Sturgeon, has blunter plates, a smoother skin, and shorter snout and cirri, 

 than the Common Sturgeon. It is frequently found more than twelve, or even fifteen, feet in length, and weighing 

 more than twelve hundred pounds. One specimen is mentioned which weighed near 3,000 pounds. Its flesh is not 

 much esteemed, and it is sometimes unwholesome ; but its air-bladder yields the very finest isinglass. It is found 

 in the Po as well as in the northern rivers. 



Several Sturgeons are found in North America, which are peculiar to that quarter of the world. 



Poliodon, may be considered as a subgenus of Accipenser. These fishes are distinguished by the great prolong- 

 ation of their snout, the broad margins of which give it the figure of a leaf. In the general form and fins they re- 

 semble the Sturgeons ; but their gill-openings are wider, and the gill-lid is prolonged in a membranous flap, which 

 extends to half the length of the body; their gape is much cleft, and furnished with a number of small teeth. 

 Their upper jaw is formed by the union of the palatals and maxillaries with a pedicle of two articulations. There is 

 a spinal cord like that in the Lamprey, and the same spiral valve which is common to most of the order ; but the 

 pancreas is partially divided into cceca. They are furnished with an air-bladder. Only a single species is known, 

 P. folium, which is found in the Mississippi. 



Chimara. — This second genus of cartilaginous fishes with free gills, closely resembles the Sharks in 

 form, and in the disposition of the fins ; but the gills open externally by one apparent hole in 

 each side, though, if we examine more closely, we find great part of their edges attached, and that the e 

 are five separate holes terminating in the common aperture : still they have a vestige of an operculum 

 concealed in the skin. Their jaws are more reduced than in the Sharks, for the palatals and tempo- 

 rals are mere simple vestiges suspended to the sides of the muzzle, and the upper jaw is represented by 

 the vomer only : hard and undivided plates supply the place of teeth, four of them above, and two below. 

 The muzzle, supported as in the Sharks, projects forwards, and has pores arranged in row? nearly 



