CLASS CRUSTACEA. 



55 



ORDER DECAPODA (de kap'6 da). 



The Stalked-eyed Crustaceans include the familiar 

 Cray-fish, the Salt-water Lobster, and the Shrimps proper. 

 The thoracic feet are in five pairs, characterizing the 

 group as Decapods (dek'a podz). The body is divided 

 into twenty segments, while the head and thorax are 

 joined together, forming a cephalo-thorax (sera lo tho'rax). 

 Though generally aquatic, a few forms have the gill 

 cavity adapted, more or less perfectly, for aerial (a e' rial) 

 respiration. The eyes are placed at the ends of movable 

 stalks. The young usually pass through a peculiar stage, 

 the Zoe'a (zo e'a).* 



FIG. 86. 



As't&cus flumftt'llis. Cray-fish, or River Lobster. 



The Cray-fish, Lobster, and Shrimp have the abdomen 

 well developed, and capable of forcibly flexing itself, 



* The terms Nauplius and Zoe'a, are taken to describe these early crustacean 

 stages, because the young, when first discovered, were thought to be adult animals, 

 and were given these generic names. 



