ASTACID^E. 71 



21. Cambarus rusticus Girard. 



Cambarus rHs:lcHs Girard, I'roc. Acail. riulaiL, T. G, p. 88. 



Fijjiiros on PI. I. ami III. 

 First abcliiiuiual logs of tho male : 



first form, tig. 80 in front ; fig. 81 out.sido. 



second form, fig. 82 in front ; fig. 83 outside. 

 Antcnnal lamina, fig. IGl, a ; cpistoma, b ; spine of the second joint of the exterior antenna, c. 



I HAVE heretofore considered the males and females from Cincinnati, 

 Ohio, which belong to C. rusiicus Gir., as a variety of C. propinqims ; the 

 rostrum, however, is never carinnted. The specimens are very closely 

 allied to C. placidus ; still, the apex of the abdominal legs is nearly 

 straight, while in C jilmkhis it is slightly incurved. 



They are very similar to G. propinquus, though the rostrum is nar- 

 rower and concave on the sides, the acumen shorter, the inner margin 

 of the hand is incui'ved, the intei'ior spine of the carpus less developed, 

 while there are two apical spines beneath, the inner one being the 

 smaller ; the brachium is more biseriated spinose beneath ; the fingers 

 are more separated at the base ; the rostrum has the acumen exca- 

 vated, not carinated ; the external part of the abdominal legs is a little 

 longer ; the posterior margin hooked as in C. obscurus ; in the female 

 there is a triangular lumen in the annulus ; the external parts of the 

 two antepenultimate segments of the postabdomen are nearly rec- 

 tangular. 



Long. Corp. 3 ; long, antenn. 2.6 ; long. ped. antic. 2.5. 



Patria : Cincinnati, Ohio. I have compared a male type, Fonna II., 

 communicated by Professor W. Stimpson. I have seen nine examples, 

 male, Formai I. and II., and female. Tlie abdominal legs in the Forma 

 II. are not articulated at the base. One male from Lake Superior seems 

 not to diffei'. 



While this species is very near to C. jilacidus, the apical parts of the 

 a1)dominal legs are shorter and more nearly straight. Nevertheless, the 

 identity is not impossible. C. ohcunis is very similar, but instantly sep- 

 arated hy the truncated epistoma. 



Cat. No. 285, Cincinnati, Ohio. Male. Fem. Spec. 12.* 



Cat. No. 187, Lake Superior, L. Agassiz. Male Form L Spec. 1. 



22. Cambarus immunis Hagen. 



Figures on V\. I., Ill, and VIII. 

 First abdominal legs of the male. 



first form, fig. 105 in front; fig. lOG outside. 

 Antcnnal lamina, fig. ICO, a; epistoma, 6; variety, d; spine of the second joint of tho exterior 



antenna^, c. 



ri. VIII. Hand. 



Mi^s. Rostro lato, dimidio longiori, supra excavato, loevi, basi foveola, 



