144 DIVISION I. VERTEBRAL ANIMALS.— CLASS IV. PISCES. 
The texture of the fins is important in classification. If the rays consist 
of single bones, whether stiff or flexible, they are said to be spinous; and, 
if they consist of a number of jointed pieces, divided at their extremities, 
they are called soft or articulated. 
The pectorals are attached to two bones immediately behind the gills, and 
answering to the scapulars, which bones are sometimes imbedded in the 
muscles, or attached to the spine, but generally to the bones of the head. 
The pelvis rarely adheres to the spine; and it is often in advance of the 
belly, and attached to the bones of the shoulders. 
The vertebra have their proximate surfaces concave, and filled with car- 
tilage, which forms the joints, and is gene rally continued by an aperture 
through the centre of each vertebra. Spinous processes, upwards and 
downwards, support the muscles, and maintain the vertical position of the 
body ; but, as far as the cavity extends, the downward processes are want- 
ing, and there are transverse processes, to which the ribs are sometimes 
soldered by cartilages. 
The head varies much in form, but, in general, consists of the same num- 
ber of bones as in the other vetebrata —a frontal of six pieces, parictals of 
three, occipitals of five, and five of sphenoid, and two of each temporal bone 
included in the composition of the cranium. 
Besides the brain, which is disposed as in reptiles, fishes have nodes, or 
ganglions, at the base of their olfactory nerves. The nostrils are simple 
cavities at the end of the muzzle, always pierced with two holes, and lined 
by a regularly-plaited pituitary membrane. In their eyes, the cornea is 
flat, and there is a little aqueous humor, but the crystalline lens is almost 
spherical, and very hard. The body is usually clothed with a scaly cover- 
ing, although there are several species which have no visible scales. 
Wonderful as it may appear to see creatures existing in a medium so 
dense that men, beasts, and birds must inevitably perish in it, yet experi- 
ence proves that, besides those species, which we are in the daily habit of 
seeing, the very depths of the immense ocean contain myriads of animated 
beings, to whose very form we are almost strangers, and of whose disposi- 
tions and manners we are still more ignorant. It is probable, indeed, that 
the fathomless recesses of the deep contain many kinds of fish that are never 
seen by man. In their construction, modes of life, and general desien, the 
watery tribes are, perhaps, still more astonishing than the inhabitants of 
either the land or the air. The structure of fish, and their adaptation to 
the element in which they are to live, are eminent proofs of divine wisdom. 
Most of them have the same external form (sharp at each end, and swelling 
in the middle), by which configuration they are enabled to traverse their 
native clement with greater case and swiftness. From their shape, men 
