132 



A COURSE ON ZOOLOGY. 



FIG. 71. 



CRAYFISH FROM ABOVE. CT, head and thorax; A, abdomen; n, internal 

 antennae ; N, external antennae ; o, eye ; PI, jaws of the first pair of walking 

 feet; P 2 to P 6 , walking feet ; a, rings of the abdomen ; pg, pieces of the tail. 



