110 A REVISION OF THE ASTACIDA. 
Male, form I. — Hooks of third pair of legs smaller; first pair of abdom- 
inal appendages thicker, bifid for but a short distance from the tip, rami 
stout, the outer one the longer, the inner one slightly incurved, swollen at 
tip, blunt pointed; very slight trace, or none, of projecting angle on ante- 
rior margin at base of the rami. 
Sternum between the fourth pair of legs smooth; anterior 
Female. 
wall of annulus ventralis largely developed, bituberculate, fossa triangular, 
posterior wall with a median, backward-projecting tubercle divided by a 
longitudinal narrow fissure. 
Length of a male, form IL, 75mm. Length of carapace, 56.5 mm. 
Length of abdomen, 36.5 mm. Length of rostrum, 8.5 mm. From tip of 
rostrum to cervical groove, 22.5 mm. From cervical groove to hind margin 
of carapace, 14 mm. Width of areola, 1.5 mm. 
Known Localities. — Pennsylvania: Pittsburg (Coll. Acad. Nat. Sci. Phila.) ; 
Philadelphia Co. [?] (Coll. Acad. Nat. Sci. Phila.). Ohio: Kelley’s Island, 
Lake Erie (Peabody Acad. Sci.); Miami River, Dayton (Coll. Acad. Nat. Sci. 
Phila.) ; Yellow Springs; Cincinnati, Ohio River. Indiana: Madison, Ohio 
River (Coll. O. P. Hay); White River (Coll. Bost. Soc. Nat. Hist.) ; Indian- 
apolis (Coll. Peabody Acad. Sci). Illinois: Quiney ; Normal (W. F. Bundy). 
Kentucky: Little Hickman, Kentucky River; Perryville, Boyle Co.; Salt 
River. Tennessee: Cumberland Gap; Lebanon. Lake Superior. Wiscon- 
sin: Racine; Beloit (W. F. Bundy); Ironton (W. F. Bundy); Fox River 
(W. F. Bundy [C. placidus]|). Towa: Lizard Creek, Fort Dodge. Missouri: 
Osage River. Arkansas: White River, Eureka Springs, Carroll Co. (Coll. 
U.S. Nat. Mus.). Texas. 
The above description is drawn up from Hagen’s types of C. rusticus 
from Cincinnati, Ohio (M. C. Z., No. 285), and from speciinens of the same 
form from Yellow Springs, Ohio (M. C. Z., No. 3427). Hagen’s type from 
Lake Superior (M. C. Z., No. 187) differs in having very long, straight fingers, 
not tuberculate on their inner margins, like C. placidus Hag. 
In the larger males, form I, from Yellow Springs, the rami of the first 
abdominal appendages are curved forwards a little at the base, and then 
recurved toward the tip, forming an are; the tip of the inner rami is con- 
siderably dilated. In very young specimens of both sexes (20 mm. long, 
or thereabouts) there is a dense beard on the interior margin of the car- 
pus and meros of the chelipeds, as well as on the inner side of the external 
finger near the base. In some specimens the fingers are long and straight. 
