88 GIANT FISHES 



Palaeopterygii (" ancient fins "), Crossopterygii (" fringed 

 fins"), and Neopterygii ("new fins"). The technical 

 differences between these groups need not bother us here, 

 but it may be mentioned that they are concerned with the 

 form of the skeleton and scales, and the structure of the 

 fins. It must be noted, however, that, as far as existing fishes 

 are concerned, these groups are of vastly different sizes. 

 The first and second of the sub-classes together include some 

 10 living genera and less than 50 species, whereas the sub-class 

 Neopterygii contains some hundreds of genera and at least 

 15,000 species. 



Since the larger Bony Fishes dealt with in this book are 

 necessarily scattered through a number of different Orders, it 

 will be impossible to treat them in quite the same way as 

 the Sharks and Rays were dealt with in the foregoing chapters. 

 Sometimes we shall be dealing with a family of fishes, some- 

 times with a genus, and at other times with a single species 

 picked out from a genus. In the present chapter are included 

 nine different kinds of fishes, belonging to five orders, but all 

 agreeing in having none of the rays supporting the fins trans- 

 formed into true spines. As a result, they may be conve- 

 niently, although somewhat unscientifically, grouped together 

 as Soft-rayed Bony Fishes. 



STURGEONS. 



(Family Acipenserid^e ; Genus Acipenser.) Fig. 33. 



The body is long and roughly circular in cross-section, and 

 the snout is produced and pointed. The head is covered with 

 closely approximated bony plates. The eyes are small, and 

 above each eye is a small spiracle. The mouth is small, 

 rounded, placed on the under-side of the head, and capable 

 of being protruded to a remarkable extent ; the jaws are 

 quite toothless. On the lower side of the snout, a little in 

 front of the mouth, is a transverse row of 4 barbels or feelers. 

 The single dorsal fin is placed far back on the body, slightly 

 in front of the anal fin and a little behind the pelvic fins, which 

 are also situated well back. All these fins have thick fleshy 

 bases where they join the body. The pectoral fins are placed 

 low down on the sides, and the front rays of each fin are fused 



