540 



ZOOLOGY 



SECT. 



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

 found in America, Australia, and New Zealand. 



External Characters. --The body of the Crayfish (Fig. 430,^4 

 and B) is divided into two regions an anterior, the cephalothorax 



snr 



six. 



FIG 



(From Lang's Comparative Anatomy.) 



Fn;. 430 JS. Transverse section of abdomen of Crayfish. DA, dorsal abdominal artery; EM, 

 dorsal muscles of the abdomen ; El', space between the plimmn and the appendage; FM, 

 ventral muscles of the abdomen ; M, muscles of the appendnge ; N, endopodite ; X(J, nerve- 

 ganglion ; P, protopodite ; PL, pleumn ; PR, hind-gut ; S, sicrnum ; T, tergum ; V, ventral 

 abdominal artery; X, exopndite. (From Parker's /',</;,/ Zoolmjti, after Marshall and Hurst. 



(dh.\ which is unjointed, and is covered by a carapace resembling 

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

 abdomen (6), which is divided into distinct segments, movable upon 



