CAMBAKUS. Ill 



Girard's description of C. nidicus is as follows : — • 



" Rostrum narrower than in both C. affinis and C. Pcalei, and, besides, 

 concave on the sides. Terminal point shorter than either of the preceding 

 species [C. pcUucidus, affniis, Orcganiis, and Pealci] ; anterior pair of abdom- 

 inal legs (in the male) elongated, slender, with their tip curved inwards, 

 whilst the same tips are straight in G. affinis, and twisted in C. pellueiduH. 

 The dorsal area is broader than in C. Pcalei. 



" Locality. — The Ohio, at Cincinnati." 



This description does not fit very well, but Dr. Hagen examined one 

 of Girard's types and ascertained its identity. 



Closely related to the above described form are Hagen's C plaeidus and 

 C. juvenilis. I find so many specimens among the material at my disposal 

 which combine characters of these three, that I am led to consider them 

 all as varieties or forms of C. rust tens. 



In the type (male, form I.) of C. placidiis, from Quincy, 111. (M. C. Z., No. 

 29G), the rostrum is longer and narrower than in the typical C. nisticus, 

 with longer acumen and lateral spines ; the hands have long, straight, non- 

 tuberculate fingers, like the C. rusticus from Lake Superior mentioned above ; 

 the rami of the first pair of abdominal ajjpendages are a little recurved, and 

 want the projecting shoulder at the base of the rami on the anterior border; 

 the antennal scale is sub truncate, with longer, apical spine. The types from 

 Lebanon, Tenn. (M. C. Z., No. 289), are second-form males and females. They 

 differ froni the Quincy specimen in having a well-develojjed internal median 

 spine on the carpus, and an acute though small lateral spine on the carapace ; 

 in some of these specimens the rostrum is slightly carinated near the tip ; the 

 external ramus of the first abdominal ajipendage, instead of being straight, 

 as in the typical C. rusticus, is a little recurved at the tip. Of the t3-pes from 

 Texas (M. C. Z., No. 170) there are now five in the Museum collection, four 

 males of the first form, one male of the second form. In three of the first 

 forms a projecting shoulder is prominently developed on the anterior border 

 of the first pair of abdominal appendages, as in C. rnsiicus and C. juvenilis ; 

 in the fourth specimen it is also present, but less marked. Two or three of 

 these examples further agree with the typical C. rusticus in the form of the 

 chela. The internal median carpal spine is strongly developed, the lateral 

 spine of the carapace small and acute, the inner row of inferior spines of 

 the meros well pronounced. The first pair of abdominal appendages in all 

 the first-form male types of C. plaeidus are a little longer than in C rusticus. 



