46 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Having received C. spelceus from Mr. Simon, I have been able to compare the two forms. It 

 seems to us that the present species belongs at least to a separate section of the genus from C. 

 (Blothrus) spelceus. This is seen not so much in the form of the body of C. spelceus (Schioedte), 

 though the cephalothorax is much narrower, as in the much greater length of the pedipalps. In 

 Chthonius paclcardii the base of the hand, when stretched back, reaches the end of the abdomen; in 

 spelceus the distal end of the secoud long joint reaches nearly to the end of the abdomen, hence the 

 pedipalps are nearly as long again as in Chthonius packardii; the third joint is very slender, and 

 three to four times as long as in C. paclcardii. The chelicerse differ but little, as they do not vary 

 much throughout the family, though they are smaller, and at the base are less swollen or pyri- 

 form, while the fingers are less bent. The legs in C. spelceus are much longer, the joints being 

 longer and slenderer. It is twice the size of our Mammoth Cave species, and in alcohol it retains 

 its bleached, white color. 



Chthonius abeillei Simon closely resembles C. spelceus, agreeing with it not only in the slender- 

 ness of the appendages, but also in the great length of the third joint of the pedipalps. Ohisium 

 (Blothrus) cerberus (Simon) also agrees with the two foregoing species in the same characters. 

 Obisium caver narum appears to connect these three species with 0. simoni Koch and the other out- 

 of-door forms. Dr. Hagen remarks that C. paclcardii is nearest allied to C. cephalotes Simon, as 

 shown by Simon's figure 20 (PI. XIX). This must be the case, as the third joint of the pedipalps is 

 short and broad and of the same form as in our G. 'paclcardii. 



Chthonius ccbcus Packard. Plate XI, figs. 4, 4a, 46, 4c. 



Chthonius ccecus Pack.,* Amer. Naturalist, xviii, 203, Feb., 1884. 



Body unusually short and broad, and the limbs short and thick ; thorax a little shorter than 

 broad, the sides parallel, slightly narrower behind than in front. The setee on the cephalothorax 

 and abdomen less distinct than in C. paclcardii, but arranged in nearly the same manner, though I 

 could hud none on the front of the cephalothorax ; the disc is free from them, as in C.packardii. The 

 eyes are entirely wanting, there being no traces whatever of them, not even any pigment-spot. 

 The general color of the body (in alcoholic specimens) the same as in C. paclcardii, the body being 

 pale horny, the abdomen whitish, the dorsal sclerites pale horn, the chelicerse reddish, and the 

 pedipalps a little paler. Cheliceise very stout and thick, considerably more so than in C. paclcardii, 

 the fingers quite blunt at the end, the thumb acute, with six distinct teeth ; the serrula much as in 

 C. paclcardii. Pedipalps unusually short, the second joint short and nearly twice as thick as in C- 

 paclcardii ; the third joint short, thick, conical, much as in C. paclcardii, except that it is somewhat 

 thicker; the mauus is very short and thick, really but little longer than the third joint; the mov- 

 able linger nearly twice as long as the maims, and with long setae; it is stout and very straight, 

 and serrulate on the inner edge. The legs are very short and thick ; the second trochanters very 

 thick ; the fourth or hinder pair of legs not much longer, if any, than the abdomen, while in C. 

 paclcardii they are fully twice as long. Abdomen of 11 segments, broad and short, with the tergal 

 sclerites rather more distinct than in C. paclcardii. 



Length of body, with the chelicerce, 1.5 ram . 



Two specimens from Weyer's Cave, Virginia. 



Remarks. — This species differs remarkably from the other cave species, being very broad 

 and short, with straighter, less curved fingers of the pedipalps, while the hind legs are scarcely 

 longer than the abdomen ; and the cephalothorax is actually shorter than broad. It is totally 

 blind, with no traces of even a pigment-spot. It is a notable exception to the law that blind 

 forms have usually a slenderer body and attenuated extremities. Unfortunately I have no 

 out-of-door species to compare it with. It agrees with the generic characters given by Simon 

 in his great work on the Arachnida of France, the cephalothorax narrowing behind, and the 

 fingers of the pedipalps being straight. It must be confessed, however, that these are very 

 slight generic characters, though Simon of course mentions others. It seems to us that the 

 three species of the suppressed genus Blothrus, i. e., B. spelceus, B. abeillii, and B. cerberus, 

 all of which have remarkably long pedipalps (the third joint being very long and slender), long 



* The article containing the description of this species was by oversight unsigned by the author's name. 



