540 



ZOOLOGY 



SECT. 



genera, but agreeing with Astacus in all essential features, are 

 found in America, -Aii§Jij;alia, and New Zealand. 



External Characters .''^rte body of the-Crayfish (Fig. 430,^ 

 and B) is divided into two regions— ^anjsuiteriorf the ce'/ihalothorax 



Fig. 430./.— Astacus fluviatilus, side view of m;ile. ai, antenuule ; a2, antenna ; a&. abdomen ; 

 cth. eephulothorax ; /a', gill-cover ; r. rostrum ; !^, third maxillipede ; 9, first leg ; 10—13, 

 remaining legs ; lit, uropod ; XIV, first abdominal segment ; XIX, sixth aladominal segment. 

 (From Lang's Comparative Anaiomy.) 



Fig. 430 B. — Transverse seetion of abdomen of Crayfish. DA, dorsal abdominal artery ; EM, 

 dorsal museles ..>f the abdomen ; EP, spaec between the pleuron and the appendage ; FM, 

 ventral muscles of the alidumen ; M, museles of the appendage ; N, endopodite ; NG, nerve- 

 ganglion ; P, protupoditc ; PL, pleurun ; PR, lund-giit ; S, siernum ; T, tergum ; V, ventral 

 abdominal artery ; X, exupodite, (From Parker's rr/iclim/ Zootor/i/, after Marshalland Hurst. 



(dh.), which is unjointed, and is covered by a cara2Kice resembling 

 that of Apus, but of smaller proportional size ; and a posterior, the 

 ahdomcn {oh), which is divided into distinct segments, movable upon 



