208 DIVISION I. VERTEBRAL ANIMALS.— CLASS IV. PISCES. 
surface of the water; and their brilliant colors sparkle in the waves like 
those of the Chetodons. 
The genera found on our shores are Monocanthus, the File-fish ; Aluteres, 
the Unicorn File-fish ; and Ostracion, the Trunk-fish. They are all small 
fishes, of singular appearance, but of no value to man. 
CHONDROPTERYGII. (Second Series of Fishes.) 
This series comprises the Cartilaginous Fishes, that is, those whose skele- 
ton has no bony fibres, but the calcareous matter disposed in grains. The 
cranium is always formed of a single piece, without sutures. The Chon- 
dropterygit divide into two orders —those witlr free gills, like all other 
fishes, and those with fixed gills, which are so attached to the skin by the 
internal edges that the water cannot escape from their intervals except by 
-holes in their surface. 
ORDER I. CHONDROPTERYGILT LIBERIS. (Free Gills.) 
This order is composed of those fishes which “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 max- 
illaries, form the upper jaw, while there are vestiges of the intermaxillaries 
in the thick lips. Placed upon a pedicle of three articulations, this mouth 
is more protractile than that of the Shark; the eyes and nostrils are on the 
sides of the head, and barbules are suspended from the muzzle; the laby- 
rinth 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 guilet 
by a large opening. Sturgeons ascend some rivers in vast numbers, and 
are the object of valuable fisheries. The flesh of most is agreeable.” 
A. Oxyrinchus. —The Sharp-Nosed Sturgeon. This is the name applied 
