SHARKS. 265 



to deposit their eggs. Their fecundity is very great. We are assured that 

 1.500,000 eggs have been found in a single female that weighed 270 Ibs., and 

 in another weighing 2,800 Ibs., the spawn alone weighed Soo Ibs. 



The young ones seek the sea very early, and remain there till full grown. 

 The flesh is wholesome ; and from their eggs a kind of food is prepared, much 

 esteemed in the north of Europe, called caviar. It is chiefly from the swim- 

 ming-bladder of these fishes that isinglass is manufactured. 



The Polyodon, or Spatularia, a fish allied to the sturgeon, is found in the 

 Mississippi : it is remarkable for an enormous prolongation of the muzzle, to 

 which its wide borders give the figure of a leaf. The mouth is well cleft and 

 furnished with several small teeth. 



The Chimseras form a connecting-link between the preceding 



and the Sharks. 



FIG. 284. NORTHERN- CH 



CHONDROPTERYGII WITH FIXED BRANCH!*. 



In this division of cartilaginous fishes the gills, instead of being 

 free on their external edge, and suspended in a common cavity, 

 from which the water escapes by a single opening, are adherent 

 to the skin, so that for the escape of the water that passes over 

 them there are as many openings as there are intervals between 

 the branchiae. In other respects these fishes differ very much 

 from each other. They are divided into two sub-orders, distin- 

 guished by the structure of their jaws, viz., 



The Plagiostoraes* and the Cyclostomes.f 



SUB-ORDER OE. TEAGIOSTOMES. 



This sub-order comprises the Sharks and the Rays or Skates. 

 They have both pectoral and ventral fins, five branchial openings 

 on each side of the neck, or on its inferior face, and jaws armed 

 with many teeth. They lay eggs covered with a hard horny shell 

 (Fig. 286). 



The Sharks (Squalidai) are recognizable by their general form, which 



* TrAcfyto?, plagios, oblique ; <rr6/za, stoma, the mouth : having their mouths placed trans- 

 versely, t KIJK\OS, cycles, a circle ; cro/za, stoma, the mouth : having circular mouths. 



