42 A REVISION OF THE ASTACID.E. 



eyed form derived from without the cave ! But as we have seen (see p. 18), 

 G. pellucidus is a very aberrant species, with no very closely related form 

 outside the cave. The simple form of the male appendages, and the com- 

 bination of characters belonging to different groups,* seen in C. peUucidiis, 

 indicate, to my mind, that it is a very ancient form, which has been preserved 

 in the seclusion of the cave, while its nearest kin succumbed in the sharper 

 struggle incident to life outside, or were replaced by modified descendants 

 evolved to meet the changeable conditions which obtain without the caverns. 

 This view is rendered more probable when one remembers that the same 

 form, C. pellucidus, occurs in the Wyandotte Cave on the other side of that 

 ancient river, the Ohio. The transportation of an eyeless cave species from 

 the Kentucky caverns to those of Indiana seems out of the question, and 

 one is driven to the conclusion that the subtei'ranean waters of both localities 

 derived this eyeless species from a similar form with well-developed eyes, 

 that peopled the streams throughout this region at a remote period. Fur- 

 ther, if we trust the statements of Gustav Joseph (see p. 45), a Candjarus is 

 found in the caves of Carniola in Southern Austria very closely related 

 to C. 2>f^/Mm7HS, while all the European ci'ayfishes else belong to another 

 genus, Astacus. That the similarity of conditions affecting cavern life in all 

 parts of the world is sufficient to bring about the close agreement between 

 the crayfishes of the caves of Carniola and Kentucky, when the forms out- 

 side the caves belong to different genera in the two localities, seems highly 

 improbable. The genus Cambarus in North America has not originated 

 under the influences of subterranean life, but is the ordinary form of cray- 

 fish throughout the whole of the eastern and central portions of the conti- 

 nent. If the cave species of Carniola were derived from the present outside 

 fauna of Europe, we should have a blind Astacus instead of a blind Cambarus. 

 I am rather inclined to accept the Carniola cave species as a witness to the 

 former existence of the genus Cambarus in the rivers of Europe (see p. 17G). 

 C. pellucidus is subject to considerable variation. In some specimens 

 the rostrum is shorter than in typical specimens, and contracts more from 

 the base to the lateral teeth, which are much less prominent. The spines 

 of the postorbital ridge and sides of the carapace are slightly developed. 

 This is the form described as a new species, Orconcctes inermis, from Wyan- 

 dotte Cave, Indiana, by Prof Cope, in 1872. I owe to Prof A. S. Packard 



* With the essential characters of Group I. arc foiiud the general form of body of the species belonging 

 to Gronp III. and the rostrum of Group IV. The anteimal scale dilated near the tip is characteristic of 

 Groups III. and IV., rather than of Group I. 



