ASTACID.E. 37 



of the tip; the tip is more sinuated, with sharper lateral teeth; the 

 hands are smaller and smoother; the femur is not tuberculated on the 

 inner side. But a closer examination of many young and old speci- 

 mens from the South shows so many analogous forms, that it is im- 

 possible, at least as yet, to separate them with certainty. But I con- 

 fess that they seem, in many respects, to belong to a different species 

 (viz. C. Blandinffu). Long. corp. 3 ad 4 inch. 



Mas maximus long. corp. G.3 ; antenn. 5.1; ped. ant, 6.2; chela 1 , 3.9. 



Patria : New Orleans and Milliken's Bend, Louisiana ; Mobile ; 

 Charleston, South Carolina ; St. Louis, Mississippi bottom ; James 

 River, Virginia (Mus. Philad.) ; Mobile River; Kemper Co., Mississippi 

 (Mus. Philad.). 



Var. A. Lawn Ridge, Basson Ridge. Evanston, and Peoria. Illinois ; 

 Indiana (Mus. Salem). 



Var. B. New Jersey ; New York ; Beaufort, North Carolina. 



Vidi specimina plurima, adulta et juniora. 



I have not seen the type of C. acutus Gir., but I have no doubt that 

 it is the first form of the species described above. The Museum of 

 Philadelphia possesses two young dry second-form males, labelled 

 " C. acutissimus Gir. ? " from Kemper Co., Mississippi, the locality men- 

 tioned by Mr. Girard for the type. There is no doubt that these males 

 are the young of the species above described, and I think also the 

 veritable C. acutissimus Gir., 1. c. T. 0, p. 91. 



Cambarus acutus is the largest North American species. The most 

 important characters are : the rostrum is one and a half times as 

 long as broad, with a distinct large impression, surrounded by a 

 little elevated part at the base ; the thorax is strongly tuberculated, 

 posteriorly dilated, without lateral spine ; the areola is impressed, very 

 little carinated in the middle; the external lobes of the two penulti- 

 mate segments of the postabdomen with the external posterior angle 

 finished in a sharp right angle ; the lamina in the middle of the apex is 

 large, the basal part longer than the apical, the terminal margin of 

 which is not very deeply excised in the middle. The antenna} are as 

 long as the body, or longer; their lamina much enlarged in the middle; 

 the external maxillary legs always barbate; the epistoma is transversely 

 elliptical, rounded in front ; the anterior legs are very long ; the 

 brachium is longer than the rostrum ; the hand has large and flat 

 tubercles, which in front are a little hairy; the external margin of the 

 hand and finger is straight; the internal margin nearly straight. 

 strongly denticulated ; the mobile finger is sinuated, a little longer 

 than the exterior; the brachium is tuberculated above and inside near 

 the carpus. The female has the venter between the fourth legs behind 

 bi- or bisbituberculated, and a larger flat tubercle near the third legs. 



The four species, C. acutus, C. Clarkii, C. troglodytes, and C. Blandingii 



