viii INTRODUCTION 



In counting the joints of a limb the first joint is 

 counted as two joints, being two small joints soldered 

 together. The first joint is that nearest the body, and 

 the first pair is the two legs nearest the eyes. The 

 eyes, antennae, antennules, and external maxillipedes are 

 considered as legs altered to discharge other duties 

 from that of walking or feeding. Of the legs of the first 

 pair, or of other pairs armed with pincer,s like them, the 

 fourth and fifth joint may be called arm and forearm ; the 

 sixth joint, the hand ; the seventh joint, the movable finger, 

 which works against a projection of the sixth joint, called 

 the fixed finger. Among some Crustacea the legs have 

 only six joints, and then there is no pincer. 



The verges are the organs of generation, and may be 

 seen on the under surface of the animal. 



The outline drawings are more or less diagramatic ; 

 the plates are from living specimens. About 421 species 

 are described. 



