76 A REVISION OF THE ASTACIDA. 
This species is unknown to me, Girard places it im his second group of 
species (C. Burtonii and allies), with toothless rostrum.and male appendages 
recurved ut their extremity. Iam inclined to think that it is a Western 
form of C. Diogenes, or possibly C. argillicola. Fort Pierre is on the right 
bank of the Missouri River, at the mouth of Bad River, within the present 
limits of the Territory of Dakota. Specimens of C. Diogenes collected at 
Cheyenne, Wyoming, have the hand broad and fingers rather short, so that 
the chela assumes a triangular shape when the fingers are closed. They 
do not differ from C. Diogenes enough to warrant a separation, but are 
very likely the form named C. Nebrascensis by Girard. I do not know 
what Hagen means when he says the hands resemble in shape those of 
C. Mexicanus. 
28. Cambarus argillicola. 
Plate IV. fig. 2. 
Cambarus argillicola, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 115, 1884. 
Rostrum short, broad, down-curved, excavated, with a deep foveola at 
base ; acumen short, broadly triangular, acute, no lateral spines. Post-orbital 
ridges without anterior spines, swollen behind. Cephalothorax laterally 
compressed, carapace punctate, anterior border not angulated, cervical 
groove sinuate, no lateral or branchiostegian spine. Areola linear in the 
middle, with an anterior and posterior triangular space, the latter the larger. 
Abdomen broad, but narrow at the base, longer than the cephalothorax. 
Telson uni- or bi-spinose on each side. Epistoma rounded in front. An- 
tennal scale small, rounded within. Third maxillipeds heavily bearded 
within, lightly so beneath. Chela large, hand swollen, denticulate on inner 
border, irregularly punctate, fingers flattened laterally, punctate and costate ; 
the movable finger has a single row of tubercles on its external border and 
a very prominent rib on its upper face; its internal, cutting edge is toothed 
and excised at the base; the outer finger is sharply marginate on its 
external border, inner border toothed and heavily bearded at the base. 
Carpus armed with a sharp spine and a few minute tubercles within; be- 
neath them is a sharp median anterior spine, and a minute spiniform tubercle 
between this and the spine of the internal border. Meros furnished with 
one or two small subapical teeth on the superior border, and two rows of 
teeth below. Second pair of legs ciliate near the end. Third pair of legs 
r 
