CRUSTACEA. 



greatly developed in some Crustaceans, such as the King- 

 crabs, and less so in the extinct Eurypterida. 



Fig. 94. Morphology of Lobster, i. Lobster with all the appendages, except the 

 terminal swimmerets, removed, and the abdominal somites separated from one another. 

 ca Carapace ; t Telson. 2. The third abdominal somite separated, t Tergum ; j Ster- 

 num ; p Pleuron ; a Propodite ; b Exopodite ; c Endopodite. 3. One of the last pair 

 of foot-jaws or maxillipedes. e Epipodite ; g Gill ; the other letters as before. 



Generally speaking, a greater or less number of the somites 

 are amalgamated together, rendering it difficult to recognise 

 their existence unless they bear appendages each pair of 

 appendages indicating a separate somite. Very commonly the 

 segments of the head and thorax are welded together into a 

 single mass, which is termed the " cephalothorax," and which 



