74 astacid^e. 



externa valida, antice impressa, apice compressa, dente valido recurvo, 

 obtuso, intus duplici. 



Vidi marem majorem pedibus abdominalibus non articulatis. 



Femina differt abdomine latiori; ventre inter pedes quartos laevi, 

 annulo trans verso, lumine posteriori piano, sulco antico longitudinali, 

 utrinque tuberculo rotundato. 



Long. corp. 3.3 ; ped. antic. 2. 



Habitat : Tennessee River, Georgia. The label is no doubt in part 

 erroneous, as no portion of the Tennessee River flows through Georgia. 



I have seen six specimens (three males, three females), of which the 

 largest was a female. The males belong to Forma IT., though the largest 

 have the abdominal legs unarticulated. Apparently the males, Forma I., 

 have larger hands and a more finished sculpture. In all the specimens 

 the whole animal is p unctuous-ciliated. The thorax is a little shorter 

 than the abdomen. 



A. affinis Say differs in having a double spine on each side of the tho- 

 rax, in the very unlike forms of the abdominal legs, in the absence of 

 the thoracic marginal spine behind the eyes, and in its larger areola. I 

 cannot discover this species in Mr. LeConte's monograph. 



It is possible that the larger female belongs to a different species ; 

 the five others are identical, the rostrum being visibly attenuated be- 

 fore, the acumen shorter, and the area broader. This female seems 

 very near C. affinis Say. The species itself is very remarkable in hav- 

 ing the abdominal legs formed exactly as in the group of C. Bartoni. 



Cat. No. 175, Tennessee River, (near the borders of?) Georgia, Colonel 

 Jones and Dr. Daniell. Male Form I. and II. Fern. Spec. 6. 



III. GROUP. (Type C. Bartonii.) 



The third legs of the males hooked ; rostrum short, toothless ; first pair of 

 abdominal legs ivith the tip of the exterior part recurved, the tip of the interior 

 part short. 



This group, perhaps, unites two groups of co-ordinate value. It is, of 

 course, possible that an examination of a greater number of specimens 

 of C. Garolinus and other allied species would allow us to place them hi 

 another different group. 



1. C. Bartonii and the allied species (except C. Garolinus and C. advena) 

 form a very natural group. Hooks only occur in the males on the third 

 pair of legs. The rostrum is short, broad, obtuse at the tip and tooth- 

 less, even in the young animals. The antennas are shorter than the 

 body ; their lamina is short and dilated near the tip ; the spine beneath 

 the first joint of the inner antennas is more apical ; the flagellum is 

 short, the inner branch a little more slender, shorter, and the joints 

 are sometimes more calcareous and fragile, similar to those of the true 



