42 A REVISION OF THE ASTACID. 
al 
eyed form derived from without the cave! But as we have seen (see p. 18), 
C. 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- 
* seen in C. pellucidus, 
bination of characters belonging to different groups, 
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 subterranean 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 Cambarus is 
found in the caves of Carniola in Southern Austria very closely related 
to C. pellucidus, while all the European crayfishes 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 eenera 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. 176). 
C. pelluadus 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, Orconectes 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. are found the general form of body of the species belonging 
to Group IIT. and the rostrum of Group ITV, ‘The antennal scale dilated near the tip is characteristic of 
Groups IIT. and IV., rather than of Group I. 
