THE PHYLUM ARTHROPODA 



341 



characterized by the exoskeleton tj-pical of arthropods, and by 

 jointed appendages, of which two pairs are mouth parts and four 

 pairs organs of locomotion. Related to the spiders are the arthro- 

 pods known as king crabs, represented by the genus Limulus. 



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Fig. 167. — A spider catching a fish. 



Some of the spiders hunt their prey instead of spinning a web and lying in wait. This 

 is an extreme instance but well authenticated, (.\fter Abraham, from drawing by Smit 

 in Natural History, 1925. Courtesy of American Museum of Natural History.) 



These are of gigantic size as compared with other existing arachnids 

 and are of special interest because they have persisted from very 

 early times without important evolutionary changes. 



