32 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



First pair of legs in the male a little slenderer than in A. communis, the second joint especially 

 much slenderer, but the hand is but slightly narrower, ^and the finger is nearly the same in the 

 female. 



First pair of male uropoda with the basal joint as long as broad, much shorter than in A. com- 

 munis; second joint not quite twice as long as broad, obliquely truncated at the end (regularly oval- 

 rounded in A. communis), with a few minute setae, while on the outside are nine setae; this group 

 not present in A. communis. Second pair minute aud short compared with those of A. communis, 

 and very different in shape (PL IV, fig. li). In the female the basal lamellate uropods oval, one- 

 third as large as the second pair, which are also oval and very thin. Caudal stylets (last pair of 

 uropoda) remarkably long and slender, between one-third and one-half the length of the body ; 

 basal joint linear; the second joint about half as long as the first and slightly more than half as 

 wide, with 8 to 10 unequal terminal bristles, of which a single external one is stouter than the 

 others and bulbous at the end ; outer branch one third to a little over one-half as long as second 

 joint, and bearing at the end three setae, flattened at the base. The great differences from the last 

 uropoda of A. communis may be seen by reference to PL III, figs, lb, 1c, and PI. IV, fig. 3g. There 

 are no auditory setae on the end of the last pair of uropoda. Length of body, male, 12 mm j width, 

 2.5 mm ; of caudal stylets, 4 mm ; the males a littie smaller than the females. 



This crustacean is abundant in the subterranean streamlets of Mammoth Cave, especially in 

 one flowing through the Labyrinth, which we have named Shaler's Brook. The females May 1, 

 1874, had eggs in the brood-pouch. It also occurred in the River Styx, in the water of River Hall, 

 and in the Dead Sea. Also in the pools in White's Cave and in Diamond Cave, as well as Salt 

 Cave. It also occurs in Wyandotte Cave, where it was first discovered by Professor Cope, who 

 named it Gecidotoea microcephala. Having, however, received Professor Cope's type- specimens 

 from Wyandotte Cave, we have been unable to find any specific differences.* A variety (PL III, 

 fig. 5a-5d) occurred in Long Cave, 2 miles from Glasgow Junction, Kentucky, in a water-trough 

 nearly 1 mile from the mouth, May 11, 1874 (Sanborn). In the female, which is blind, the body 

 is considerably broader, the head broader if not shorter, and the abdomen is shorter than in the 

 Mammoth Cave form. Fig. 5a represents the first antenna, which has but 8 to 9 joints, and there 

 are slight differences in the anterior feet (Fig. 5d). 



From Walnut Hill Spring Cave, near Glasgow Junction, at a point 300 yards from day- 

 light, May 16, specimens were collected by Mr. Sanborn ; others collected by Mr. Sanborn in day- 

 light, 50 feet from the entrance of Walnut Hill Spring Cave, Glasgow Junction, May 14, proved 

 to exhibit no differences from Mammoth Cave forms. The first antennae (Figs. 6, 6a) have 10 joints. 



Those collected by us in Bradford Cave, Indiana, were exactly like the longer slenderer forms 

 from Mammoth Cave. Fig. 7 represents the ten jointed first antenna. , 



The Carter Cave specimens agree with those from Mammoth Cave, except that the first antennae 

 are much better developed, being larger and with several more joints (15 in all); moreover, there 

 are as many as 5 olfactory rods, the first one on the seventh joint from the base (Figs. 8, 8a). The 

 first pair of feet (PL IV, fig. 2) do not differ from those from Mammoth Cave. 



We have received numerous specimens from wells in Illinois through the kindness of Mr. S. A. 

 Forbes. They have narrower, more linear bodies than those in Mammoth Cave. They were ll mm 

 in length and 2 mm in width. 



According to Forbes's sketches (his PL I, figs. 19, 20), the two pairs of male abdominal append- 

 ages are somewhat slenderer than in our Mammoth Cave specimens. Forbes also states that the 

 first (upper) have 10 to 12 jointed flagella, " having a slender olfactory club at tip of each of the four 

 or five joints preceding the last. * * * The lower antennae are about two-thirds as long as the 

 body in the female, in the male somewhat longer," the flagellurn containing 75 to 80 joints. Forbes 

 also remarks that the length of the rami of the caudal stylets varies greatly with age and sex, 

 11 In many old males the inner is very long and the outer minute." 



Mr. Forbes adds to his description that it " is found quite frequently in deep wells of central 

 Illinois in company with, but much more abundant than, Crangonyx mucronatus. After a long 

 period of heavy rains during the last summer had greatly swelled the subterranean streams which 



* See Fifth Rep., Peab Acad. Sci., Salem, 95, 1873. 



