ASTACUS NIGRESCENS. 



245 



There are no cervical spines, and the middle part of 

 the cervical groove is angulated backwards instead of 

 being transverse. 



FIG. 62. A & D, Astacns torrent ium ; B & E, A. ndbilis ; C & F, 

 A. nigrescens. A C, 1st abdominal appendage of the male ; D F, 

 endopodite of second appendage ( x 3). a, anterior, and >, posterior rolled 

 edge : c, d, e, corresponding- parts of the appendages in each species ; 

 /, rolled plate of endopodite ; g, terminal division of endopodite. 



The abdominal pleura are narrow, equal-sided, and 

 acutely pointed in the males (fig. 61, F) slightly 

 broader, more obtuse, and with the anterior edges 



