628 NORTH AMERICAN ASTACIDE—FAXON. 
In connection with Miss Hoppin’s observations on the ecrepuscular 
habits of this species it is interesting to note that the atrophy of the 
visual organs has not progressed so far asin the other blind ecrayfishes 
of the United States, C. pellucidus and C. hamulatus.* In other respects, 
also, O. setosus is more closely related to outside, eyed species than 
is either of the other cave species. This doubtless results either from 
the twilight conditions under which it lives, or more probably from its 
having been subjected for a shorter period of time to cavern influences. 
The three blind species, although belonging to two sections of the 
genus, resemble each other in the slenderness of the body and claws 
and in the width of the antennal scale. The slenderness ofthe body and 
claws in these species may be attributed to their life in caves, where 
competition is largely removed and physical power ceases to be an im- 
portant factor in their existence. The width of the antennal scale is 
probably a variation correlated to the atrophy of the adjacent eye and 
ocular peduncle. In short, these points of resemblance between the 
three cave species, like the rudimentary state of the eye and the trans- 
parency of the shell, are of little value from a taxonomic point of view, 
not indicating close genetic affinity, but surely appearing in widely 
diverse species, provided they be subjected to the same subterranean 
life. The closer superficial likeness between C. pellucidus and C. hamu- 
latus, belonging to different sections of the genus, than between C. ham- 
ulatus and C. setosus belonging to the same section, may be explained 
by the longer period of time during which the subterranean influences 
have probably been exerted upon the first two species. 
G. C. Broadhead (Report of the Geological Survey of the State of 
Missouri, 1874, p. 36) states that blind cray fishes are found in the cave 
region of Christian County, near Ozark, in southern Missouri. It is 
probable, from the locality, that they are the same species as those 
from Jasper County. 
Cambarus affinis (Say). 
Additional localities: Shenandoah River, Waynesborough, Virginia; 
Blackwater River, Zuni, Virginia; Patoka River, Patoka, Indiana. 
D. 8. Jordan (U.S. F. C.). 
The specimens from Patoka, Indiana (six males, form I; four females), 
differ from the typical C. affinis as follows: The areola is broader in the 
middle, there is but one lateral thoracic spine, the hepatic area is 
smoother (merely granulate, instead of spinous), the branchiostegian 
*On the contrary, Mr. G. H. Parker concludes that the histology of the retina 
shows more degeneration in C. setosus than in C. pellucidus. His researches on the 
subject will shortly be published in the Bulletin of the Museum of Comparative 
Zodlogy. From the external morphology alone, one would surely be justified in 
deeming C. setosus the least modified of the three blind species. The eye-stalk and 
external part of the eye are largest in C. setosus, smallest in C. pellucidus. C. hamu- 
latus stands between the other two in this regard. For the aberrant position of C. 
pellucidus in other respects, see my Revision of the Astacidz, page 18. 
