Fig. 17. — Astacvs fliiviatilis.—A., one of the podobranchiae from the 

 outer side ; B, the same from the inner side ; C, one of the arthro- 

 branchise ; D, a part of one of the coxopoditic setas ; E, extremity of 

 the same seta ; F, extremity of a seta from the base of the podo- 

 branchia ; G, hooked seta of the lamina ; (A — C, x 3 ; D — G, highly 

 magnified), b, base of podobranchia ; cs, coxopoditic setse; cxp, 

 ooxopodite ; I, lamina, pi, plume, and st, stem of podobranchia ; 

 t, tubercle on the ooxopodite, to which the setae are attached. 



