162 



THE MORPHOLOGY OF THE COMMON CBAYFISH. 



gether with the sudden widening of the same parts in 

 the posterior cephalic 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 thorax. The three pair 

 of maxiUipedes (7, 8, 9), the forceps {10), the ambulatory 



"JIJIU 



Fig. 43. — Astacus flweiatilis.—'LaagtixiAixiaX section of the anterior part 

 of the oephalothorax ( x 3). I — IX, sterna of first nine cephalo- 

 thoracio somites; 1, eyestalk ; 2, basal joint of antennule ; 5, basal 

 joint of antenna ; 4, mandible ; a, inner division of the masticatory 

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

 attachment ; cp, free edge of carapace ; e, endostemite ; enpl, endo- 

 pleurite j epm, epimeral plate ; I, labrum ; m, muscular fibres con- 

 necting epimera with interior of carapace ; mt, metastoma ; pep. 

 procephalic process. 



