100 



MOLLUSKS 



Sepia (se'pi-a), has ten arms or tentacles, two long and 

 eight short. It moves itself forward rapidly by shooting 

 out water from a siphon in the collar region. When 

 pursued, the squid ejects an ink-like fluid which clouds 

 the water, concealing it from its prey and facilitating its 

 escape. 



Cuttle fishes are similar to squids, the marked differences 

 being in the shape of fins, the form of the eyes, and the 

 shape of the longer tentacles. 



The octopi are the largest members of the group. They 

 have eight tentacles, which in some cases reach a length of 

 thirty feet. The stories about the size and 

 behavior of the octopi are often exaggerated. 

 102. Economic Importance of the Group. — 

 Clams, scallops, oysters, and snails are used 

 as food in all parts of the world. In this 

 country, oysters are gathered in great 

 abundance from Chesapeake Bay and other 

 bays along the Atlantic Coast. 



The edible clams are of two kinds. The 

 round clam, Venus mercenaria (Ve'nus 

 mer-se-na/ri-a), is more generally used as 

 food, but the other kind, the soft-shelled 

 clam, Mya arenaria (Mi'a ar-en-a/ri-a), is 

 eaten extensively near the seashore. The 

 soft-shelled clam has a long siphon which 

 may be extended several inches beyond the 

 valves (Figure 101). 



The scallop (skol'lup) is another mollusk 

 that is eaten near the shore more extensively 

 than elsewhere. This mollusk has but one adductor 

 muscle, which is the edible portion. 



Clams and oysters are raised artificially and regularly 

 planted on natural feeding grounds. Care is taken to 



Figure 101. 



Soft-shell 



Clam. 



a, b, siphons; m, 

 mantle; s, shell; 

 /, foot. 



