280 PISCES. 



found to exceed twelve and fifteen feet in length, and to weigh 

 more than twelve hundred pounds. One specimen was cap- 

 tured whose weight amounted to near three thousand pounds. 

 The flesh is not much esteemed, and is sometimes unwholesome, 

 but the finest isinglass is made from its natatory bladder. It 

 is also found in the Po. 



North America has several species of this genus which are 

 peculiar to it.(l) 



PoLYODON, Lac. — Spatularia, Sh. 



These fishes are recognized at once by the enormous prolongation 

 of their snout, to which its broad borders give the figure of a leaf. 

 Their general form and the position of their fins, remind the ob- 

 server of a Sturgeon, but their gills are still more open, and the 

 operculum is prolonged into a membranous point which extends to 

 near the middle of the body. The mouth is well cleft and furnished 

 with numerous small teeth. Their upper jaw is formed by the union 

 of the palatines with the maxillaries, aud the pedicle has two arti- 

 culations. The spine of the back is furnished with a cord like that 

 of the lamprey; and the spiral valve, common to almost all the Chon- 

 dropterygii, is found in the intestine, but the pancreas begins to be 

 divided into caeca — they have a natatory bladder. 



But a single species is known, the Polyodon feuille, Lacep., 



I, xii, 3; Squatus spatula, Manduit, Journ. de Phys. 1774, pi. 



II. From the Mississippi. 



Chimera, Lin. (2) 



The Chimserae are closely allied to the Sharks in their general form 

 and in the position of their fins, but all their branchiae open exter- 

 nally by a single apparent hole on each side, although if we penetrate 

 more deeply, we find that they are attached by a large part of their 

 edges, and that in fact there are five particular holes terminating in 

 the bottom of the common aperture. A vestige of an operculum, 

 however, is concealed under the skin. The jaws are still more re- 

 duced than in the Shark, for the palatine and tympanic bones are 



(1) Acip. oxyrhynchus, Lesueur, Amer. Philos. Trans, new series, vol. I, p. 

 394; — Jlcip. brevirostris. Id. lb. 390; Ac. rulicundus, Id. lb. 388, and pi. xii, which 

 appears to bear a close resemblance to the Sterlet; — Ac. maculosus. Id. lb., 392, 

 appFoaches the Common Sturgeon. 



(2) This name was given to them on account of their fantastic figure, which, 

 when they are carelessly dried, as was the case with the specimens first repre- 

 sented by Clusius, Aldrovandus, Sec, appears monstrous. . 



