CRAWFISH AND LOBSTER. 



131 



does not appear separated from the body as in the insects, 

 but is combined with the thorax, and hence this part is called 

 the cephalo-thorax, as in the spiders. The cephalo-thorax is 

 covered by a continuous shield, or shell, called the carapace, 

 while the abdomen is divided into a series of segments. This 

 part can be bent snugly beneath the body (see Fig. 121). 



FIG. 121. FRESH-WATER CRAWFISH FROM THE MISSISSIPPI EIVER. 



At the hinder end of the abdomen are five flattened ap- 

 pendages, which serve as fins, by means of which the animal 

 can swim vigorously backward. (See Fig. 122.) 



FIG. 122. TAIL OF CRAWFISH SHOWING FLATTENED APPENDAGES FOR SWIMMING. 



There are two compound eyes in front, which rest upon 

 little jointed stalks, so that the creature can turn them in 

 various directions. 



