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THE CRAYFISH 



LESS. XXVII 



dm. 



artm ji ji /j. t,rw.m, /C 



aH/m 



h'lG. 84. — Diagram illustrating the action of the abdominal muscles 

 in the Crayfish. A shows the position in extension, H in flexion. 



Four abdominal segments are shown in sagittal section : tg, terga ; 

 St, sterna ; art. in, tergal articular membranes ; art. /«', sternal articular 

 membranes ; h. hinges. 



The muscles are represented as narrow bands (comp. Fig. 86 for their 

 actual dimensions), and their arrangement is greatly simplified, d.tn, 

 dorsal muscles ; c.vt, central muscle giving off extensor slips (ex) ; 

 env. til, enveloping muscles continued into anterior (/I) and posterior 

 (/?') flexor slips. 



(From Parker and Haswell's Zoo'ogy.) 



abdomen upon the cephalothorax, causing the crayfish to 

 dart backwards with great rapidity. 



