CHAPTER V. 
FISHES DIVISIBLE INTO TWO CLASSES. 
The fishes may be divided with greater ease, the 
chief character being in the skeleton. 1st, the osseous 
or bony fishes, which are commonly and emphatically 
known as fishes ; and 2ndly, the chondropterygians or car¬ 
tilaginous fishes, as sharks, rays, &c. “ The chondropte¬ 
rygians,” observes Cuvier, “ can be considered as neither 
superior nor inferior to the series of ordinary fishes, for 
several of the genera approach the reptiles in the confor¬ 
mation of the ear and genital organs, while in others the 
organization is so simple and the skeleton so much re¬ 
duced that we might be excused for hesitating to place 
them among vertebrated animals at all. They therefore 
constitute a series somewhat similar to the first , as the 
Marsupials for instance hear a resemblance to the other 
unguiculated Mammalia. The skeleton of the chondrop¬ 
terygians is essentially cartilaginous, i. e. it contains no 
osseous fibres, the calcareous matter being deposited in 
small grains, and not in filaments, — hence the absence of 
sutures in their cranium, which is always formed of a sin¬ 
gle piece, but in which, by means of projections, depres¬ 
sions and holes, regions analogous to those of the cranium 
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