CLASS PISCES. 591 



good, and is sometimes even unwholesome. With 

 the natatory bladder of this fish the best isinglass is 

 made. It also ascends into the river Po. 



North America possesses several species of stur- 

 geon peculiar to itself 1 . 



Polyodon, Lac, Spatularia, Sh., 



Are directly recognized by an enormous prolongation 

 of their muzzle, to which its widened edges give the 

 figure of the leaf of a tree. Their general form, and 

 the position of their gills, resemble those of the stur- 

 geons ; but their gills are still more open, and their 

 operculum is prolonged into a membranaceous point, 

 which is extended as far as the middle of the body. 

 Their mouth is very much cleft, and furnished with 

 many small teeth. The upper jaw is formed of the 

 union of the palatines to the maxillaries, and the 

 pedicle has two articulations. The spine of the 

 back has a cord like that of the lamprey. We find 

 in the intestine the spiral valvule, common to almost 

 all the chondropterygii, but the pancreas commences 

 to be divided into cceca. There is a natatory bladder. 

 But a single species is known, from the Mississippi, 

 Polyodon fe?rille, Lac. I. xii. 3 ; Squalus spatula, 

 Mauduit. Journ. de Phys. Nov. 1774. pi. ii. 



1 Acip. oxyrhyncus, Lesueur, Araer. Trans., new series, vol. i. 

 p. 394. Ac. brevirostris, Id. ib. 390. Ac. rubicundus, Id. ib. 

 388 ; and pi. xii. which appears very much to resemble the sterlet. 

 Ac. maculosus, Id. ib. 392, very much approaches the common 

 sturgeon. 



