no A EEVISIOX OF THE ASTACID.E. 



Male, form II. — Hooks of third pair of legs smaller ; first pair of abdom- 

 inal appendages thicker, bilid for but a sliort distance from the tip, rami 

 stout, the outer one the longer, the inner one slighll^y incurved, swollen at 

 tip, blunt pointed ; very slight trace, or none, of projecting angle on ante- 

 rior margin at base of the rami. 



Female. — Sternnm between the fourth pair of legs smooth ; anterior 

 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 II., 73 mm. Length of carapace, 36.-5 mm. 

 Length of abdomen, 36.5 mm. Length of rostrum, 8.5 nun. 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 Locnlllles. — 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. 0. P. Hay); White River (Coll. Bost. Soc. Nat. Hist.); Indian- 

 apolis (Coll. Peabody Acad. Sci.). Illinois : Quincy ; Normal (W. F. Bundy). 

 Kentucky: Little Hickman, Kentucky River; Perry ville, Boyle Co.; Salt 

 River. Tennes.see : Cumberland Gap ; Lebanon. Lake Superior. Wiscon- 

 sin : Racine; Beloit (W. F. Bundy); Ironton (W. F. Bundy); Fox River 

 [W . Y . ^imi\y \_C . 2^lacidus]). Iowa: 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 rusiicus 

 from Cincinnati, Ohio (M. C. Z., No. 285), and from specimens 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 arc ; 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 extei'nal 

 finger near the base. In some specimens the fingers are long and straight. 



