160 



INTRODUCTION TO ZOOLOGY 



q to 1 3 legs. 



Swimmerers. 



Fig. 96. — The Appendages of the Prawn re- 

 moved from one side of the body and 

 arranged in order. 



The other thoracic 

 legs, belonging to seg- 

 ments 9 to 13, are the 

 most conspicuous of all, 

 and are known as the 

 " walking legs." In 

 most Decapods they are 

 all long and strong and 

 seven -jointed, and the 

 first two legs end in a 

 little pincer-like claw ; 

 in the prawn, however, 

 the first pair of " walk- 

 ing legs " is relatively 

 thin and delicate, and 

 is turned forward on 

 the top of the "jaw 

 feet," lying doubled over 

 just behind them, whilst 

 the second pair is the 

 largest of all, and bears 

 the efficient pincers 

 (chelae), with which the 

 creature catches its prey. 

 This is so in the Com- 

 mon Shrimp (Crangon 

 vulgaris) also, but in the 

 lobsters, crayfish, and 

 crabs it is the first walk- 

 ing legs that are speci- 

 ally enlarged, and bear 

 the large pinching claws. 



The abdominal appen- 

 dages are modified for 

 swimming. They are 

 relatively short, and 

 each is two - branched, 

 the branches being 

 fringed with hairs ; the 

 first five pairs, which 

 are all much alike, are 



