OT 
a ground feeder. All the cartilaginous fishes are 
ground feeders. he flattened head, the transversal 
mouth, forming when open, a circumference, equal 
to one third the length of the fish as in the plagos- 
tome division, or the truncated head and the suc~ 
torial mouth, without teeth, as in the cyclostomes, 
fit them only for taking their prey from banks, and 
shallows. Besides this, they all want the swimming 
bladder, so that they fall to the bottom of the water 
as soon as they cease to move init. ‘I‘here is 
not so much mystery in the vast schools of sharks 
that are sometimes seen in places, as naturalists 
suppose. They congregate on the shoals for breeding. 
The saunterer on the shingled beach, however in- 
different he may be to seaweeds, and such common 
products of the surf, scarce fails to be attracted by 
the semi-transparent, rolled-up sheets of something, 
having neither the appearance of horn nor parchs 
ment, though resembling both, which he hears called 
mermaids’ purses. He takes it in his hand, or per- 
haps turns it over with his foot. He is puzzled by 
its strange box-like character, with convoluted ten- 
drils at the corners. ‘They are tangled with the 
seaweed. ‘They were placed among the vegetation of 
the shore, to be fastened by those corner strings that 
ihey might not wash away into deep water. They 
are the egg-cases of cartilaginous fishes, deposited 
there to be hatched in the warm and sunny shallows. 
Anybody who has sent down the leaded line, armed 
with fish-hooks, when crossing the banks of New- 
foundland, knows that he is just as likely to bring 
