38 ASTACIDiE. 



are very similar in size and forms. For C Blandingii see the descrip- 

 tion of this species. Of the three other species, the thorax is more 

 ovoid, more dilated in C. acutus ; laterally more compressed in C. Clarkii ; 

 between the two in C troglodytes, nearly as dilated as in the first, but a 

 little more depressed. The areola is the broadest, but very narrow in 

 C. acutus, the narrowest and the most shallow in 0. Clarldi ; in both 

 species the areola is posteriorly much more dilated than anteriorly ; in 

 C. troglodytes the areola is nearly as broad posteriorly as anteriorly. 

 The thorax is strongly tuberculated in C. acutus and C Clarkii, granu- 

 lated in C troglodytes. The rostrum is most sinuated, and often 

 clearly dentated in C. Clarldi; less sinuated and dentated in C troglody- 

 tes. The rostrum is nearly plain in C. troglodytes, most excavated, with 

 the margins more elevated, in C. Clarldi; C. acutus is intermediate. 

 The base of the rostrum shows a different structure, but a little obscure. 

 There is in C acutus and C. Clarldi a circular depression, terminated in 

 front by a somewhat rounded elevation in C. acutus ; in C. Clarldi by 

 two oblique straight elevations, united in an obtuse angle ; in C. troglo- 

 dytes there is in the circular depression a very flat, central, round eleva- 

 tion or tubercle. The postabdomen is the narrowest and laterally most 

 compressed in C. Clarldi ; the apical part of the lamina is longer in 

 C. troglodytes than in the other species. The hands are the shortest 

 and broadest in C. troglodytes ; the fingers nearly as long as the hands, 

 in the other species much longer, in C. Clarldi they are deflected. The 

 movable annulus in the female of C troglodytes is striking ; it is very 

 firmly united with the venter between the fourth legs in the two other 

 species. 



Cat. No. 1161, New Orleans, La., L. Agassiz. Mas. Form I. Fern. 

 Specimens, 12.* 



Cat. No. 1843, New Orleans, La., L. Agassiz. Mas. very large, Form I. 

 Spec. 1. 



Cat. No. 1844, New Orleans, La., L. Agassiz. Mas. Form I. and II. 

 Fern. Spec. 12.* 



Cat. No. 1845, New Orleans, La., L. Agassiz. Mas. Form II. ; first pair 

 of abdominal legs articulated or not articulated. Spec. 12.* 



Cat. No. 291, Mobile, Ala., L. Agassiz. Mas. Form I. and II. Fern. 

 Spec. 12 * 



Cat. No. 1846, Mobile, Ala., L. Agassiz. Mas. Form I. and II. Fern, 

 var. thorace lEeviori. Spec. 12* 



Cat. No. 182, Charleston, S. C, L. Agassiz. Fem. Spec. 1. 



Cat. No. 274, St. Louis, Mo., Dr. Engelmann. Mas. young. Spec. 1. 



Cat. No. 151, St. Louis, Mississippi bottom, Dr. Engelmann. Mas. 

 Form I. Fem. Spec. 6. 



Var. A. Cat. No. 214, Lawn Ridge, 111., Mr. 0. Ordway. Mas. Form I. 

 and II. Fem. Spec. 12 * 



* The star signifies that the Museum possesses more than 12 specimens. 



