CRAYFISH, L(JBSTEK,S, Hl'IDEKS, AND INSECTS 125 



into segments similar to the body of an earthworm. The 

 cephalothorax is also segmented; but the segmentation is 

 obscuretl on the dor- 

 sal surface by the 

 carapace, but shows 

 plainly on the ventral 

 side. 



The appendages of 

 the abdomen. — Each 

 segment of the abdo- 

 men (in the male), 

 except the last, bears 

 a pair of appendages 

 known as the siuim- 

 merets. These are 

 small, segmented, leg- 

 like organs held close 

 under the abdomen. 

 \\dth the exception of 

 the last pair. These 

 are broad and flat, 

 and, together with 



Fig. GS. — Crayfi.sli. 



the last segment of the abdomen, the /e/.w?i, form the tail 

 fin, or smmmingfin. In the female, the first two pairs of 

 swimmerets are either very small or altogether lacking. 



Appendages of the cephalothorax, — The appendages of 

 the cephalothorax nia.v lie divided into fiA^e groups: the 

 walking legs, five pairs; the foot jaws, or niaxillipeds, three 

 pairs; the .jaws, two pairs of maxilla? and one pair of man- 

 dibles; the antenntc, or feelers, one pair; and the antennules, 

 .one pair. 



The walking legs are attached to the thorax and each 



