MEMOIKS OE THE NATIONAL ACADEMY OF SCIENCES. 63 



formiug a truncated angular spine, and not much more than half as long as the outer lamina; hetween the inner 

 and outer lamina, its base next to the inner lamina, is a middle spine ending in an irregular tuft of fine spinules. 



The genus is distinguished from Tricbopetalum by its want of eyes, its broader head, its long slender body, 

 \\ ltb long set;e, by the eighth pair of female rudimentary legs ending in a claw. From Zygonopus it differs in the 

 shorter sixth antennal joint, its broader head, its slenderer legs, the sixth pair in the female not being unlike the 

 others, and by the more prominent shoulders aud longer setae. The species of the two genera are of the same general 

 form and size. 



The genus Scoterpos was proposed by Professor Cope for the present species in the American Naturalist for July, 

 1872, page 414. The very brief and incomplete characters given are the " lack of eyes and of lateral pores ; " the 

 absence of the latter having been "asserted by Dr. Packard." Ignorant of the difference between the Mammoth 

 Cave blind Myriopod and Lysiopetalum, the latter being the only genus of the family then known, we referred it to 

 the geuus Spirostrephou. 



Scoterpes copei Cope. Plate VIII, figs. 1, la-lm. 



Spirostrephou (Pseudotremia) copei Packard, Amer. Naturalist, v, 748. December, 1871. 



Scoterpes copei Cope, Amer. Naturalist, vi, 414, July, 1872. 



Spirostrephou copei Harger, Amer. Journ. Sci., iv, August, 1872. 



Spirostrephou copei Packard, Zoology, edit. 1-3, le>79-'81. 



Scoterpes copei Pack., Proc. Amer. Phil. Soc, xxi, 193, 1883. 

 About twenty males and females examined. Body white, with no dusky discoloratious ; thirty segments besides 

 the head in specimens ll mm in length; and fifty-two pairs of legs ; iu one female individual 8 mm long there were 

 forty-uine pairs of legs, including the eighth or rudimentary pair ; iu other individuals 6 mm long there were twenty-four 

 segments behind the head. The head is provided with short, fine, erect hairs of different lengths, especially on the 

 sides of the genae. Iu the absence of a secoud species we can not distinguish all the specific from the generic char- 

 acters. For minor specific characters the reader is referred to the figures. 

 The males and females are alike in size and form. 



The specimens were most abundant in the Labyrinth in Mammoth Cave, but also occurred in other localities in 

 the cave. It is also common in Diamond Cave, where I collected it, and was discovered by Mr. Sanborn in Poynter's 

 Cave, 300 yards from daylight. In one of the specimens from the last- mentioned cave the antenna? were rather more 

 slender rhan usual. 



The genus Scoterpes and its single species copei appears to be limited to Mammoth Cave and the others near, in 

 apparently the same system of caves. It was erroneously reported by me to occur in Weyer's and the Luray caves, as 

 the specimens collected belong to Zygonopus whitei. Without doubt the genus is a modified Tricbopetalum, which has 

 become longer and slenderer in body, with longer legs and antennae, as well as setae ; whether it is a descendant of 

 Triehopetahim lunatum or not is uncertain; it may have descended from a different species, but there seems to be no 

 reasonable doubt but that, it is a modified form of a small hairy Lysiopetaloid form, with antenna? exactly like those 

 of Trichopetaluiu. (For details of which genus see Plate VII, figs. 2, 2a-2f.) 



Zygonopus Ryder. 



Zygonopus Ryder, Proc. U. S. Nat. Mus., iii, 527, February 16, 1881. 

 Zygonopus Pack., Proc. Amer. Phil. Soc, xxi, 194, 1883. 



Body rather slenderer than in Scoterpes. The head ditt'ers from that of Scoterpes in being much narrower and 

 higher, the swollen sides or genaa being much less swollen ; the vertex is swollen ; the front as broad as long, with the 

 upper edge a little- hollowed, but quite distinct from the vertex itself. The eyes entirely wanting, as in Scoterpes. 

 The antennae are rather thick, and in this respect approach Scoterpes, but the sixth and seventh joints are much longer 

 aud rather more setose ; the sixth joint is about two-thirds as thick as long, and the last (seventh) joint nearly twice 

 as long as thick. The sides of the segments are swollen subdorsally as in Scoterpes, aud the setiferous tubercles are 

 arranged as iu that genus, but the setae are shorter; the lower posterior edges of the arthromeres below the shoulder 

 or hump is chased obliquely with tine impressed lines. The feet are less iu number than in Scoterpes. The diagnostic 

 characters of the genus lie in the remarkably swollen sixth pair of feet of the male, iu which the second joint is rather 

 thick, while the third joint is long, and with the fourth joint remarkably swollen, with a series of about nine oblique 

 retractor muscles diverging from the proximal end of the terminal joint, which is long and slender and straight, with a 

 v. ill-developed claw. The seventh pair of the male are of the normal form. The rudimentary or eighth pair are like 

 those of Trichopetalum, the second (terminal) joint not ending in a claw, thus differing from those of Scoterpes. The 

 male genital armature is entirely unlike that of Scoterpes, though it is rudimentary and minute; the outer lamina 

 consists of a basal subtriangnlar portion, ending in a long, slender, curved spine, beneath which is a stouter spine, 

 shorter and less curved; a minute median setose lamina is present, while the inner lamina is a weak, slender, setose 

 filamentary outgrowth. 



Mr. Ryder's gineric characters are stated very briefly, as follows : " Sixth pair of legs very robust, and with the 

 third joint greatly swollen." The generic characters are not contrasted by him with those of Scoterpes. 



This genus differs from Scoterpes in the remarkably swollen, clasping, sixth pair of legs and in the male genital 

 armature, while either sex differs 1'roui Scoterpes iu the much, narrower head and longer sixth aud seventh antennal 

 joints, 



