THE OLD RED SANDSTONE. 59 
the sense of sight; they seem mere worms, furnished with 
fins and gills, and were so classed by Linnzus; but though 
now ascertained to be in reality fishes, they must be regarded 
as the lowest link in the scale —as connecting the class with 
the class Vermes, just as the superior cartilaginous fishes may 
be regarded as connecting it with the class Reptilia. 
Between the osseous and the cartilaginous fishes there ex- 
ist some very striking dissimilarities. ‘The skull of the osse- 
ous fish is divided into a greater number of distinct bones, 
and possesses more movable parts, than the skulls of mam- 
miferous animals: the skull of the cartilaginous fish, on the 
contrary, consists of but a single piece, without joint or sut- 
ure. There is another marked distinction. The bony fish, 
if it approaches in form to that general type which we recog- 
nize amid all the varieties of the class as proper to fishes, 
and to which, in all their families, nature is continually in- 
clining, will be found to have a tail branching out, as in the 
perch and herring, from the bone in which the vertebral col- 
umn terminates; whereas the cartilaginous fish, if it also 
approach the general type, will be found to have a tail 
formed, as in the sturgeon and dog-fish, on both sides of the 
hinder portion of the spine, but developed much more largely 
on the under than on the upper side. In some instances, it 
is wanting on the upper side altogether. It may be as im- 
possible to assign reasons for such relations as for those 
families seem better established. Of a pair of gigantic rays (Cepha- 
loptera giorna) taken in the Mediterranean, and described by Risso, 
the female was captured by some fishermen; and the male continued 
constantly about the boat, as if bewailing the fate of his companion, 
and was then found floating dead. — See Wilson’s article IcurHyoLo- 
cx, Encyc. Brit., seventh edition. 
6 * 
