1881.] The Fauna of the Nickajack Cave. 879 
a very little light from the movth was distinguishable. These 
were the common blob, Potamocottus meridionalis, and sucker, 
Catostomus teres. 
Ata distance of a mile from the mouth, the blind crawfish, 
Orconectes hamulatus, began to be abundant; their snowy white 
forms being readily distinguished by candle light in the clear 
water. . 
On the land the Spirostrephon cavernarum proved to be com- 
mon in some places, especially near to bat excrement, where were 
also found a number of Pselaphid beetles. 
On examination of the aquatic cave life, it appears that of the 
five kinds of animals found living in the waters of the cave, all but 
one differ decidedly from those of the caves of Kentucky, Indi- 
ana or Virginia. This is a matter of considerable interest from an 
evolutional point of view, as it shows that these cave forms are 
the descendants of different out-of-door species from those of tlie 
caves to the northward. The Nickajack cave may be in a different 
faunal region from the Mammoth or Wyandotte caves, and thus 
the blind crawfish has perhaps originated from a different species 
of Cambarus than that which gave origin to Orconectes pellucidus, 
Thus while the conditions, such as dryness and temperature, of 
cave life are much the same throughout the United States, the 
ancestors of the different cave animals were, in most cases, distinct, 
since they belonged to somewhat different zoo-geographical areas. 
The first animal to notice, and one not uncommon in the waters 
of the cave, is a little Isopod Crustacean which is evidently a modi- 
fied Asellus, or water wood-louse, of the same genus as that so 
abundant in the caves, subterranean streams and wells of Indiana 
and Kentucky. We originally described the Mammoth cave 
form as Cecidotea stygia Packard; our new species may be called 
Cecidotea nickajackensis Packard} 
Jt is eyeless, and the bo ly is longer, narrower and slenderer than in C. stygia. 
The first antennze are very long and reach tu the end of the third joint of the second 
antennz ; they are nearly twice as long as in C. styy¢z, and are purplish white, while 
the flagellum is provided with long hairs, The second antennee are as long as the 
head and extend backwards as far as the base of the abdomen, The legs are much 
longer and slenderer than in C. s/yg?a. The abdomen is long and narrow, and the 
caudal appendages are moderately long in one specimen and short in another ; in 
one individual the outer branch is much shorter and smaller than in the others, and 
in most it is as‘long as the basal joint. On the whole the caudal appendages are no 
longer than the telson or terminal segment of the abdomen, while in C. stygéaz they 
are half as long as the entire body, Length 6 mm, 
