40 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



This species was also found by Mr. J. B. Proctor to occur in Bat Cave, Edmonsou county, 

 Kentucky, June 13, 1874. It does not differ from Mammoth Cave examples. The larger hand is 

 on the left side. One female collected by Mr. Sanborn in a cave near Haunted Cave, same county 

 and State, was rather small, but presented no differences from Mammoth Cave females. 



In none of the specimens examined did the rudimentary eyes seem to vary. 



Relation of 0. pellucidus to out-of-door species of Cambarus. — In comparing pellucidus with C. 

 bartonii, a young male of Form II, 1.30 inches long, from Mammoth Cave, it was found to differ from 

 6. bartonii in the spinules on each side of the apex of the rostrum. 



It seems to us that 0. pellucidus is, in the proportions of the body and particularly the shape 

 of the rostrum more like G. bartonii thau G. affinis. C. pellucidus differs from G. bartonii in the 

 longer hand and the fourth joint of the limb, while the thorax and rostrum are much longer. The 

 antennae are rather the stouter and shorter in G. pellucidus. The elongated body, long hands, 

 and the limbs bearing them are changes such as we would expect to meet with in cave animals. 



The 0. bartonii, which is a good deal bleached, is as white and as pale as the pellucidus, except 

 that the head and first pair of limbs and hands have scattered blackish speckles. G. affinis is 

 evidently, however, the parent form of G. pellucidus. On comparing males of Form II of the two 

 species, C. pellucidus has stouter and larger second antennae; the antennal scale is broader at the 

 end, the rostrum is wider, the head is rather wider and shorter, the hinder edge is less convex, the 

 thorax is a third longer, the abdomen but slightly longer, the difference being in the cephalo- 

 thorax. The ischium of first pair of legs is one third as thick and about one-third as long, the 

 meros one-half as thick and one-third longer; the carpus is of about the same length, but the 

 hand is one-half as wide and a little longer than in G. affinis. Of the four succeeding pairs of feet 

 the ischia are about the same length, the meros somewhat longer. The first antennae are longer 

 and slenderer. 



The gouopods in Form II are very distinct from the out of door species, being nearly one-halt 

 shorter. 



Cambarus rusticus, which is closely related to G. affinis, was found by us in abundance at a 

 point only about 20 feet from the mouth of the cave in the brooks which flow out of Bradford 

 Cave; inside of the cave pellucidus is not uncommon. 



Remarks. — Two alternatives present themselves in considering the origin of the form pellu- 

 cidus. First, it either is derived, with G. affinis, from a common ancester; or second, and what 

 seems more probable, it is a modification of G. affinis or an allied species, e. g., rusticus. The 

 characteristics which separate G. pellucidus from C. affinis or C. bartonii or any out-of-door species 

 are those which have been induced by its life in total darkness and the diminution in its food- 

 supply. The close neighborhood of the habitat of the two forms at the Bradford Cave, the blind 

 one living only a few yards away and in the upper part of the same brook as C. rusticus, is very 

 significant, and this affords us the best means of ascertaining the origin of this form. It is paral- 

 leled by the probable origin of the Myriopod Scoterpes from Trichopetalum and of Pseudotremia 

 from Lysiopetalum. 



Cambarus hamtjlattjs (Cope and Packard). 



Orconeotes hamulatus Cope aud Packard, Amer. Naturalist, xv, 881, PI. vii, figs. 1, la, 16, Nov., 1881. 

 Cambarus hamulatus Faxon, Proc. Airier. Acad. Arts arid Sci., xx, 145, 1884 ; Revision of the Astacidie, Mem. 

 Mus. Comp. Zool., x, 4, 81. PI. iv, fig. 6, ix, figs, la, la', Aug.. 1885. 



In this species the epistoma is much as that of C. bartonii, but shorter and broader ; while the 

 median terminal tooth is less marked than in G. latimanus, and the sides fall away rapidly from 

 the front margin. It is entirely different in shape from that of G. pellucidus. The antennal lamina 

 is shorter, broader, and much more rounded on the inner edge thau in G. pellucidus, and in this re- 

 spect differs from C. latimanus. The rostrum is narrower than in G. pellucidus, while the first pair 

 of (large) claws are much slenderer, and the telson narrower than in G. pellucidus. The most ob- 

 vious difference is seen in the modified first and second pairs of abdominal feet of the male, to 

 which we may apply the term gonopod, for it is not properly an intromittent organ.* The first 

 and second pair of gonopods differ decidedly from those of G. pellucidus, and closely resemble 

 those of Form II of Cambarus latimanus (from Athens, Georgia, figured by Hagen), those of the 



