MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 29 



is serrate, the teeth being like those of a saw, conical, with the bases approximate. Eyes distinct, 

 broader than long, blackish, situated directly in front of the stomach ; the latter being short, 

 pyriforin. The intestine, as usual, long and straight. 



The first antennae of the male composed of eight very uuequal joints, the two basal shorter than 

 thick, the second with three spines ■ third joint very short, less than half as long as the first, and 

 with the distal end oblique, and with a stout spine; fourth joiut large, much swollen, as long as 

 the second and third together, and with a row of slender seta? on the inner side ; fifth joint small, 

 two- thirds as thick and as long as the fourth ; sixth long and slender, one-half as thick as the fourth ; 

 the seventh and eighth much slenderer than the sixth ; the eighth (terminal one) considerably 

 shorter than the seventh, and tipped with three hairs. Second antennae three-jointed, basal joint 

 short, no longer than bi'oad ; second and third joints subequal, of about the same length and thick- 

 ness; from the base of the second a sleuder curved joint arises, which is about one-third as thick 

 as the second joint, and gives origin to four large setae ; third joint subclavate, with about six hairs, 

 besides four long terminal setae, which are flattened and bent in the middle, with the ends hair-like. 



In the first pair of feet the outer branch consists of rather short joints, shorter than those of 

 the inner ramus, which is 3 jointed and nearly twice as long as the outer. 



The feet in general are rather long, with large, long spines. The fourth arthromere behind 

 the carapace bears a pair of tapering triarticulate rudimentary feet as long as the segment itself, 

 and ending in hooks. The succeeding segment only bears a pair of two unequal stout setae. 

 Caudal seta; not more than one-third longer than the appendages themselves, which are conical 

 and of the usual form ; the inner pair are twice as long as the outer ; the setae are stiff and stout, 

 simple, with no hairs. No spines on the terminal segment betweeu the caudal appendages; only a 

 few fine minute hairs. Color of the body and appendages, snow white. 



Length, .03 mm (or gV inch.) 



This species differs from C. cryptornm and C. staphylinus, mt7iutus 7 and rostratm of Europe in 

 the simple caudal setae and the large coarse spines on the edges of the arthromeres. 



In its general appearance, and especially the form of the male antennae, the present species is 

 much nearer allied to C. cryptornm Brady than to the other European species figured. 



Several specimens occurred in water taken from Wandering Willie's Spring. The intestines 

 were filled with a dark mass of food, and the dejections were elongated pyriform. This spring is 

 probably fed from pools above, or the water percolates from above down into the spring. Whether 

 this species of Copepod is peculiar to the cave or carried down into the cavern each year from 

 out-of-doors remains to be seen when the Copepod fauna of the water in the neighborhood of 

 Mammoth Cave has been thoroughly investigated. 



Family ASELLID^E. 

 C^eoidot^ea stygia Packard. PI. Ill, IV, figs. 1, la-lm. 



CfFcidota'a stygia Packard, Ainer. Naturalist, v. 752, Figs. 132, 133, 1871. 



Crecidotcea microcephala Cope, Arner. Naturalist, vi. 411, 419, Figs. 109, 110, July, 1872; " Mammoth Cave and 



its Inhabitants", etc., 19, 1872; Annals and Mag. Nat. Hist., Nov., 1871 (no name). 

 Caddotcea stygia Pack., 5th Rep. Peab. Acad. Sc, Salem, 95, 1873; Smith, U. S. Com. Fish and Fisheries, II. 



Report for 1872 and 1873, 661, 1874. 

 Asellus stygius Forbes, Bull. Illinois Mus. Nat. Hist., I, 11, 1876. 

 < oiidotwa stygia Hubbard, Amer. Ent., HI; Fig. 10, p. 79, March, 1880. 



Generic characters. — Differs from Asellus in the much longer body, the absence of eyes, and 

 in the longer and narrower head. The second (larger) antennae are almost as long as the body; 

 in Asellus only one-half or a little more than one-half as long as the body; the fifth joint nearly 

 twice as long as the fourth ; in Asellus it is but slightly longer than the fourth. The legs are also 

 slenderer, the terminal joint much narrower, aud the claws much smaller. The telson (abdomen) 

 is very long aud narrow, oblong, two-thirds as broad as long; whereas in Asellus it is not so long 

 as broad, and is much rounded. The mouth parts also present some differences; the lobes of the 

 maxilla are narrower ; the penultimate joint of the palpus of the maxillipedes are one-half as thick 



