THE LIVING WORLD. 
81 
skate. They differ from the shark chiefly in having ventral instead of 
lateral gill-clefts. With its long, flat body the ray covers its prey, and while 
thus holding it down, uses its singular ventral jaws for the conversion of its 
prey into food. Some species are oviparous, and others bring forth their young 
alive; the eggs, which may frequently be found on the beach, are called sea- 
purses. During its youth the ray resembles the shark, but as it matures it 
develops disproportionately its pectoral fins and changes to a rayed form. It 
has no distinct head; the tail is long, and slender; it has two dorsal fins, and 
sometimes a caudal one. The great size of the pectoral fins is responsible for 
the singular form of the fish ; its powerful jaws are filled with teeth which 
point back¬ 
wards, and 
they can be 
protruded at 
pleasure. 
The Bor¬ 
dered Ray, 
theRaiaBa- 
tis (notably), 
the Thorn- 
back, and 
the Clear¬ 
nosed Ray, 
are not un- 
frequently to 
be found in 
our markets. 
The Sea 
Porcupine 
swells itself 
up with air 
until it be¬ 
comes tem¬ 
porarily 
powe rless, 
and floats 
around, belly 
upward, un¬ 
til it is final¬ 
ly successful 
in expelling 
its incon¬ 
venient SUp- dog fish ( Squalus acanthias) and sea hound ( Mustelus cattis). 
ply. 
The Balloon Fish is frequently found on the coast of the United States. 
It is supplied with long, sharp spines which inflict the most poisonous wounds. 
The Puffer, or Swell Fish, is likewise a source of danger to fishermen, 
who frequently catch them with the hook, or find them entrapped in their nets. 
The Electric Ray (Torpedo vulgaris) weighs upwards of a hundred 
6 
