86 
MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
character, and some specimens of G. gracilis from Lake Superior actually have only one or two 
more segments than the subterranean species. In the antennae there are no constant differences. 
There are some very slight differences in the first and second pairs of legs, especially in the 
females, but not greater than usually exist in the individuals of a single species in allied genera, 
and any large series of specimens would undoubtedly show all the intermediate forms. In the 
third to the seventh pairs of legs there is a constant difference in ali*the specimens examined, the 
spines being more numerous, longer, and more slender in G. gracilis. The spines upon the first 
and second pairs of caudal stylets are a little shorter and more obtuse in G. packardii than they 
usually are in G. gracilis; otherwise there is no difference in the caudal stylets and telson. 
These differences are all such as very naturally lead to the supposition that this subterranean 
form has been derived from the G. gracilis at no very remote period, although this supposition 
may well be held in reserve until we have a more complete series of the subterranean species for 
comparison. G. gracilis occurs as far south as Grand Rapids, Michigan, whence we have received 
specimens from Mr. N. Coleman, and it very likely occurs in the same region as G. packardii. 
The figures are all from Professor Packard’s original specimens, collected from wells in 
Orleans, Indiana, by Dr. Moses N. Elrod. Only one of these has the body entire; this is a female, 
5 . 5 mm long, from which Figs, o to 8 were made. A larger specimen, a female about 7.5 mm long, 
unfortunately wanting most of the antennulse and antenna;, collected from a well at New Albany, 
Indiana, by Dr. John Sloan, was sent to Dr. Packard for examination. 
Figs. 5 to 11.— Crangonyx packardii, details all enlarged 48 diameters; 5 to 8 , female, 5.5 mm 
long; 9 to 11, female, about 7.5 mm long: 5, lateral view of head; 6 , terminal portion of one of the 
first pair of legs, outside; 7, same of second pair; 8 , terminal portion of abdomen, lateral view; 9, 
one of the first pair of legs, outside; 10 , one of second pair of legs, outside; 11 , antennula and 
antenna, side view. [All the figures, 1 to 11, drawn by Prof. S. I. Smith.] 
Crangonyx antennatus Pack. 
_— Crangonyx antennatus Pack., Amer. Naturalist, xv, 880, 1881. 
The second crustacean discovered swimming about in the subterranean stream of Nickajack 
Cave was a species of Amphipod belonging to the genus Crangonyx, and has been described as 
Fig. 5.— Crangonyx antennatus Packard, a, end of abdomen and appendages; b, head, with base ot upper aDd entire lower antennae and 
eyes; c, manus of second pair of feet; all enlarged. 
Crangonyx antennatus Packard. * It is a large purplish species, with very long antennae, and dis¬ 
tinct, well-developed black eyes. 
* It is a large and purplish species; the first antennm very long; the flagellum with 20 to 24 joints ; the entire 
antennae being over one-half and nearly two-thirds as long as the body; the last joint of the peduncle being slightly 
more than half as long as the penultimate joint. Compared with C. gracilis Smith, from Lake Superior, it differs in 
the form of the eyes, the longer and stouter first antennae, the fiageilum having a greater number of joints, and in the 
different proportions of the joints of the peduncle; the second joint of the latter being much longer than in C. gracilis, 
while the first joint of the scape is much longer, and the second and third joints one-third longer in proportion than 
in C. gracilis. The fourth pair of epimera are unusually large and nearly square. The telson, together with the caudal 
stylets, is much as in C. gracilis, hut the rami are slightly stouter and more polished, and the spinules a little stouter. 
It probably is a little larger species than C. gracilis, the specimens being 6 to 7 mm in length; the eyes are not so 
distinct, and are ouly oue-fourth as large as in C. gracilis. It is very different from C. vitreus (Cope), of Mammoth 
Cave, and from C. packardii Smith, differing in its distinct eyes, and larger, more numerously-jointed antennm. 
