162 



THE MOEPHOLOGY OF THE COMMON CRAYFISH. 



gether with tlie sudden widening of the same parts in 

 the posterior cephalic somites, gives rise to the hiteral 

 depression (fig. 39, (;/') in which the scaphognathite lies. 

 The limit thus indicated corresponds with that marked 

 b}^ the cervical groove upon the surface of the carapace, 

 and separates the head from the thorax. The three pair 

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



JJ.C.J^. 



Fig. 4;>. — AMacnx fluriatiJis. — Longitudinal section of the anterior part 

 of the cephalothorax ( x 8). / — IX, sterna of first nine cephalo- 

 thoracic somites; 1, eyestalk ; i', basal joint of antennule ; 5, basal 

 joint of antenna ; 4> mandible ; a, inner division of the m.asticatory 

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

 attachment ; cj), free edge of carapace : e, endosternite ; eiipJ, endo- 

 pleurite ; f/5»(. epimeral jilate ; /, labrum ; ;«, muscular fibres con- 

 necting epimera witli interior of cai'apace ; mf, metastoma ; jtcj/. 

 procephalic process. 



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