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 antenne (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. spnosus. 
GROUP IV. (Tyrr, 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. viril’s 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, Sloanit, lan- 
cifer, propinquus, and Harrison’, 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, Alabamensis, Palmeri, Mississippiensis, 
and compressus the distal part of the long rami is strongly recurved. In 
“CO. 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, antennal scales, 
and chele also mark @. 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 O. medius, C. immunis, and C. Mississippiensis the margins of the rostrum 
are entire, at least in full-grown individuals. 
This group corresponds to Hagen’s Group II. 
The following artificial key may aid in the determination of the species 
in this group. 
