162 



THE MORPHOLOGY OF THE COMMON CKAYFISH. 



gether witli the sudden widening" of tlie same parts in 

 the posterioi" cephaHc somites, gives rise to the lateral 

 depression (fig. 39, cf) in which the scaphognathite lies. 

 The limit thus indicated corresponds with that marked 

 by the cervical groove upon the surface of the carapace, 

 and separates the head from the tliorax. The three pair 

 of maxillipedes {7, 8, 9), the forceps [10), the ambulatory 



J":f 



Fjg. 4?.. — Axtdciix flur'udllis. — Longitudinal section of the anterior part 

 of the cephalothorax ( x ;>). / — IX, sterna of first nine cei^halo- 

 thoracic somites; 1, eyestalk ; 2, basal joint of antennule ; 3, basal 

 joint of antenna ; ^, mandible; w. inner division of the masticatorj' 

 surface of the mandible ; u', apophysis of the mandible for muscular 

 attachment ; rp, free edge of carapace : e, endosternite ; enpl, endo- 

 pleurite ; c^/w. epimeral plate ; /, labrum ; w, muscular fibres con- 

 necting- epiniera with interior of carapace; mt. nietastoma ; prp. 

 procephalic process. 



