314 



GENERAL BIOLOGY 



terior to it, so modified as to form jaws. The two pair of maxillae and 

 the three pair of maxillipeds, together with the mandible, thus make six 

 pairs of jaws altogether. 



Back of these six jaws, a pair of pincers is attached to the thorax 

 proper. These are known as chelipeds ( ), and be- 



hind the chelipeds are four pair of walking legs. By observing these 

 legs it will be noticed that they are very much akin to the cheale proper 

 in that each has a broad attachment, the protopodite ( ), 



Fig. 203. 



A. Mandible. B. First maxilla. C. Second maxilla. 

 bs. Basipodite. ex. Coxopodite. en. Endopodite. ep. Epipodite. 

 ex. Exopodite. sc. Scaphognathite. 



D. and E. First and second Maxillipedes. br. Branchial 

 filaments, cp. Carpopodite. dp. Dactylopodite. is. Ischiopodite. 

 me. Meropodite. prp. Propodite portions of endopodite. 



F. Third Maxillipede. cs. Coxopodite setae. 



G. Gill (=;epipodite.) (After Latter.) 



where it meets the body, composed of two portions, a coxopodite 

 ( ) and a basipodite ( ) which 



then join the pincer proper. These pincers consist of a solid immovable 

 portion, the exopodite ( ) and a smaller movable and 



inner portion, the endopodite ( ). 



It will be observed that the pincers are only an enlarged walking 

 leg. 



The portion of the crayfish directly behind the cephalothorax, with 

 the definite segmentation, is known as the abdomen and consists of six 

 segments, beside the tail. This latter consists of a central portion of the 

 tail called the telson ( ), and two pairs of leaf-like 



structures on each side called uropods, which assist in forming a broad 

 wing-like tail and which, when the crayfish is frightened, can be bent 



