CRUSTACEA. 



515 



seven in the second, three to four times the third, and two or three 

 times the fourth year. In the fifth year they attain the adult state. 

 Whence it follows, that the small lobsters served at our tables have 

 changed their calcareous vestment something like twenty-one times, 

 and are now clothed in their twenty-second habit. 



The species of crabs are numerous, and they vary in size. The 



Fig. 344. — Corystes Cassivelaunus, female. 



long-clawed crab {Corystes Cassivelaunus) of Pennant and Leach 

 (Fig. 343) is remarkable for its long antennse, which considerably 

 exceed the body. The foot-jaws have their third joint longer than 

 the second, terminating in an obtuse point, with a notch on its 

 interior edge ; eyes wide apart, borne upon large peduncles, which 

 are short and nearly cylindrical ; anterior feet large, equal, twice the 

 length of the body, and nearly cylindrical in the males ; in the 

 females (Fig. 344) about the length of the body, and compressed, 

 especially towards the hand-claw. The other feet terminate in an 



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