208
_
'
THE SEAS
known as the gill-rakers (Plate 76).
These are best developed in the Basking shark, a tropical sh which spends its
life near the surface feeding on small animals. The bottom—
living sh, such as the atsh and rays, live upon the
worms and _shellsh of various kinds which they seize and
—
.
crush up with their powerful jaws.
It, is because the
Dogger Bank has an exceptionally —— rich fauna of‘bivalve
molluscs
which
are
found in great patches sometimes
fty miles by twenty, and at a density of between 1,000
and 8,000 per square metre, that the Bank forms such an
ideal ”region f0r the growth of plaiee.
The rays are often"
able to crush up the massive shells of the larger bivalves
-
such as the oyster, one of their number forming the most
serious enemy of the pearl oyster on the Ceylon beds——
yet not an enemy to the_pearl diver for this ray is the
second host of the tapeworm, the; early stages of ,which
live in the pearl oyster and often form the nucleus round
which pearls are formed.
Other rays do serious damage
to the deeper—water oysters off the eastern coast of North
America. -More actively swimming shes such as the cod and
haddock also feed on the bottom animals.
Other shes
pursue their
small relatives
the, herring
shoals
for
_
instance are invariably accompanied by great numbers
of dog—sh which annually devour large numbers of herring.
'
More._unique are the feeding habits of the Angler, a sluggish
sh which lives on the seabottom and has a short stunpy
.
tail, a comparatively small body and an immense head
and broad mouth with inwardly pointed, hinged teeth.
Above the mouth is a slender spine, the modied rst ray of
the. dorsal n, with a tufted end ;; the Angler lies per—
fectly still with its huge mouth shut and daintil»y waving
this tentacle ‘as a hire ; thus, far from having tb hunt their
.
prey, sh of all
impelled by curiosity or_ desire for
‘
f00d, come to inspect the 1ure and are s'eized. in a moment
_
'
THE SEAS
known as the gill-rakers (Plate 76).
These are best developed in the Basking shark, a tropical sh which spends its
life near the surface feeding on small animals. The bottom—
living sh, such as the atsh and rays, live upon the
worms and _shellsh of various kinds which they seize and
—
.
crush up with their powerful jaws.
It, is because the
Dogger Bank has an exceptionally —— rich fauna of‘bivalve
molluscs
which
are
found in great patches sometimes
fty miles by twenty, and at a density of between 1,000
and 8,000 per square metre, that the Bank forms such an
ideal ”region f0r the growth of plaiee.
The rays are often"
able to crush up the massive shells of the larger bivalves
-
such as the oyster, one of their number forming the most
serious enemy of the pearl oyster on the Ceylon beds——
yet not an enemy to the_pearl diver for this ray is the
second host of the tapeworm, the; early stages of ,which
live in the pearl oyster and often form the nucleus round
which pearls are formed.
Other rays do serious damage
to the deeper—water oysters off the eastern coast of North
America. -More actively swimming shes such as the cod and
haddock also feed on the bottom animals.
Other shes
pursue their
small relatives
the, herring
shoals
for
_
instance are invariably accompanied by great numbers
of dog—sh which annually devour large numbers of herring.
'
More._unique are the feeding habits of the Angler, a sluggish
sh which lives on the seabottom and has a short stunpy
.
tail, a comparatively small body and an immense head
and broad mouth with inwardly pointed, hinged teeth.
Above the mouth is a slender spine, the modied rst ray of
the. dorsal n, with a tufted end ;; the Angler lies per—
fectly still with its huge mouth shut and daintil»y waving
this tentacle ‘as a hire ; thus, far from having tb hunt their
.
prey, sh of all
impelled by curiosity or_ desire for
‘
f00d, come to inspect the 1ure and are s'eized. in a moment