ISOPODA ASELLID^E. 77 



abundant. C. stygia suffers also from the blind fish. The stomachs of 

 blind fishes examined contained C. stygia and in one case remains of 

 this species formed almost the entire stomach contents. This isopod is 

 rendered scarce in the larger pools, where the blind fishes are most 

 numerous, but is abundant in the more shallow parts of the stream 

 near by. I have never seen it feed, but judging from its habits, its food 

 is probably decaying organic matter. Individuals kept in the laboratory 

 feed upon decaying leaves in the water. Females with young in the 

 brood pouch have been taken at different seasons, and quite small indi- 

 viduals are seen at all times, so that this species must breed throughout 

 the year. I now have this species breeding in the light. 



As already indicated, this species seems generally distributed in sub- 

 terranean waters in this region and often appears at the outlet of under- 

 ground waters. I have found it in Mayfield's, Twin, and Mammoth 

 caves. Outside of caves I have found it near Bloomington in a spring 

 and its stream, and also in a sheltered ravine. 



Packard (1888, 108-110) studied the structure of the eyes of C. stygia 

 and found that in every case the optic ganglia and optic nerves are 

 missing. In nearly every case the "retinal cells" are broken and in 

 many cases the lenses and pigment are entirely lacking. Specimens from 

 a well in Illinois have the pigments and some of the lenses still present, 

 but in Mammoth Cave specimens this last trace of the eye is gone. 



Cascidotea nickajackensis Packard (1881, 879) is known from Nicka- 

 jack Cave in Tennessee and from southern Georgia. C. richardsonas 

 Hay (19026, 424) also occurs in Nickajack Cave. C. smithii Ulrich 

 (1901, 93) comes from an artesian well at San Marcos, Texas. These 

 species of Csecidotea are white and eyeless. The genus resembles 

 Asellus very closely and it seems probable that the species of Csecidotea 

 have been derived from species of Asellus. Asellus cavaticus Schiodte 

 is found in caves, springs, and wells in different parts of Europe, and 

 Asellus forelii Blanc occurs in the depths of Lake Geneva. Both species 

 are white. The former is eyeless and the latter is eyeless or with 

 rudimentary eyes. Asellus hoppinse Faxon (cf. Garman, 1889, 232) is 

 described from Day's Cave, Missouri. 



Family ONISCIDAE. 

 Porcellio scaber Latrielle. 



LATRIELLE, Hist. Crust. Ins., VH, 1804, 45. RICHARDSON, Bull. U. S. Nat. Mus. 54, 

 1905, 621, fig. 671. 



A single specimen was found upon the wall at "6" during April. 

 It was not bleached in the least. 



Blatchley (1896, 234) found a specimen of this genus near the mouth 

 of Little Wyandotte Cave. Garman (1889, 237) reports one of this 



