astacid^e. 71 



21. Cambaeus eusttcus Girard. 



Cambarus rusiicus Girard, Proc. Acad. Philad., T. 6, p. 88. 



Figures on PI. I. and III. 



First abdominal legs of the male : 



first form, fig. 80 in front ; fig. 81 outside. 



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

 Antennal lamina, fig. 161, a ; epistoma, 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 O. rusticus Gir., as a variety of C. propinquits ; the 

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

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

 straight, while in C. piacidus it is slightly incurved. 



They are very similar to C. propinquits, though the rostrum is nar- 

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

 of the hand is incurved, the interior 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. obscuras ; 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, Forma II., 

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

 male, Formee I. and II., and female. The abdominal legs in the Forma 

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

 not to differ. 



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

 abdominal legs are shorter and more nearly straight. Nevertheless, the 

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

 arated by the truncated epistoma. 



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



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



22. Cambaeus immunis Hagen. 



Figures on PI. I., III., and VIII. 



First abdominal legs of the male. 



first form, fig. 105 in front; fig. 106 outside. 

 Antennal lamina, fig. 160, a ; epistoma, b ; variety, d; spine of the second joint of the exterior 



antennae, c. 



PI. VIII. Hand. 



Mas. Rostro lato, dimidio longiori, supra excavato, laevi, basi foveola, 



