CAMBARUS. 85 



versity, Irvington, Ind. It was collected by Jordan in the Etowah River, 

 at Rome, Ga. It measures 3| inches in length. The areola in this specimen 

 is a little longer and less dilated posteriorly than in the types from the 

 Tennessee River. 



The antenna 1 (mutilated in the type specimens) are nearly as long as 

 the body. 



C. extraneus has been found in but two localities, in both places in com- 

 pany with C. spiriosus. 



GROUP IV. (Type, C. affinis.) 



Third segment of the third pair of legs of the male hooked. First abdominal 

 appendages of the male bifid, terminated by two nearly straight styliform branches. 



Rarely a specimen of C virilis and C. propinquus is found with hooks on 

 the third segment of the second, as well as the third, pair of legs, but 

 normally only the third legs are provided with hooks. 



The first pair of abdominal appendages in the male are bifid, ending 

 in two free styliform rami. The rami are short, so that the tips reach 

 forward only to the base of the third pair of legs in C affinis, Sloanii, lan- 

 cifer, propinquus, and Harrisonii, while in the other species of the group the 

 rami are elongated to such a degree that they reach forward as far as 

 the base of the second pair of legs, or even to the chelipeds when the 

 abdomen is flexed. In C. immunis, Aldbamensis, Palmeri, Mississippiensis, 

 and compressus the distal part of the long rami is strongly recurved. In 

 0. lancifer the terminal rami are short, the outer part almost tooth-like, 

 so that the character of the appendage approaches the type seen in the 

 species belonging to Group I. The shape of the rostrum, antenna] scales, 

 and chela? also mark C. lancifer as a passage form between Group I. and 

 Group IV. 



The rostrum is commonly armed with a lateral spine in this group, but 

 in G. matins, ('. immunis, and C. Mississippiensis the margins of the rostrum 

 are entire, at least in full-grown individuals. 



This group corresponds to Eagen's Group II. 



The following artificial key may aid in the determination of the species 

 in this group. 



