TABLE SHOWING THE CLASSIFICATION OF THE CEPHALOPODS 
DESCRIBED IN THIS CHAPTER 
CLASS CEPHALOPODA 
Subclasses Orders Genera Species 
Tetrabranchiata Nautilus 
Octopus 
OCTOPODA { Argonne ree 
Dibranchiata Spirula 
DECAPODA § Ommastrephes 0, illecebrosus 
( Sepia L. Pealet 
Loligo ; L. brevis 
CLASS CEPHALOPODA 
The Cephalopoda form a singularly isolated group, and are so 
superior in organization and intelligence to all other mollusks 
that it is difficult to believe that they are first cousins to the 
lethargic gasteropod and the simply constructed bivalve. But 
the class bears the stamp of its origin in a mantle, a radula, and 
a disposition of internal organs and functions which, although 
highly perfected, is essentially molluscan. 
Along the Atlantic coast of the United States, particularly in 
its northern portion, occur several examples of cephalopods be- 
longing to the genera Ommastrephes and Loligo, all the species of 
which are referred to, in common parlance, as “squids.” They 
frequent shallow water, and are often to be found in weirs, dart- 
ing about with rapid, spasmodic movements, or perhaps lying 
motionless on the bottom. The squids enter the weirs for the 
purpose of capturing the young mackerel which are caught in 
these traps. The squid lies quietly upon the bottom, which it 
simulates so closely in color as to be almost invisible, and when 
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