CARTILAGINOUS FISHES. 
291 
ORDER IV. CARTILAGINEI. 
{Cartilaginous Fishes.^ 
The largest and most formidable of all fishes 
are found in this Order. The peculiar struc- 
ture of their skeleton, which gives rise to their 
name, admits of these animals continuing to grow 
as long as they live ; the consequence of which 
is, that as they inhabit the wide ocean, and have 
few enemies, they are sometimes met with of such 
an enormous size that their weight and dimen- 
sions are almost incredible.”^ 
The great essential character of the Order is 
the nature of their skeleton. Their bones have 
but a very small quantity of earthy matter in 
their composition ; and what is present is deposit- 
ed in grains, and not in distinct fibres. The 
skull is not divided into separate bones, but is 
formed in a single piece ; yet ridges, furrows, 
and holes on its surfaces, enable the anatomist 
to discover the portions, which in other fishes 
are distinct, though here soldered, as it were, 
together. Even bones, that in other fishes con- 
stitute moveable joints, are not always distinct 
in this Order ; the verteirce or j oints of the spine, 
for example, are, in some of the Hays, united into 
a single mass ; and in other genera, some of the 
bones of the face are quite wanting. The bones 
of the jaws, known to anatomists under the names 
* Swainson, Nat. Hist, of Fishes, i. 118. 
