62 
MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
Var .carterensis. A decided approach to S. laotarius is seen in certaiu brown specimens, only partly bleached 
found in the Carter caves, Kentucky, viz: Bat Cave, X Cave, and Zwingle’s Cave, besides a cave across the road 
from the hotel, which is used as an ice-house. 
In the specimens from Bat Cave the antennae are slightly shorter, and a little slenderer, particularly joints 3 to 
5; but joint 7 is much shorter and blunter than in the Bradford Cave individuals; the antenn®, however, are of the 
same length, though slenderer than those living in Great Wyandotte Cave. The eyes form a nearly equilaterally 
triangular area, with from twenty-three to twenty-five facets. The segments behind the head are 30. Thev differ 
from the Wyandotte examples in the posterior or swollen portion being rather more prominent than in the former 
forming more marked lateral swellings, with about eight ridges on the side of each boss, and the body is larger and 
thicker, but the legs are of the same length. 
The head is dark in front, mottled above and below with paler horn color. The antenn® are concolorous with 
the head and body, but the terminal joints are paler, as are the legs, which are also paler at the articulations. The 
entire body is dark horo-brown, mottled and irregularly lineated. 
The smoother anterior portion of the scuta shows a tendency to be paler than the tuberculated portion and of a 
bluish-gray tint. The tubercles are no more prominent than in the Wyandotte individuals. 
The segments in both the Wyandotte species and var. carterensis rapidly decrease in size, the penultimate 
segment being pointed, and each segment is provided with regular, high-raised, parallel, prominent ridges on the 
shoulder or lateral boss; about forty to forty-five on a scutum on the sixth segment from the end of the body. 
Length, 23 mm ; thickness, 2.5 mm ; the body being considerably larger and thicker than in the Wyandotte 
specimens. (See figs. 2, 2a-2c.) 
Two specimens from X Cave are exactly in size and color like those from Bat Cave. 
Three specimens from the ice-house cave only differ from those in Bat Cave in being somewhat paler but the 
eyes and antenn® are the same. 
A large and a partly grown one from Zwingle’s Cave was collected by Mr. Sanborn August 23; these were 
also paler than those from Bat Cave. With them were associated a Ceuthophilus, with eyes well developed and 
a Polydesmus. 
This form or variety would be, perhaps, mistaken for Lysiopetalum laotarium, but it is true in all the generic 
details to Pseudotremia; at the same time it is what may be called a twilight species, living in small caves in 
situations partially lighted. It is probably derived from L. laotarium, or a closely-allied species. We doubt if it will 
ever be found living in the same situations as X. laotarium. 
It is evident that the var. carterensis is the ancestral form of the now fixed species P. caver- 
narum, and that the former has been derived either from L. laotarium, or from an allied species; 
hence the genus Pseudotremia has been probably derived from the genus Lysiopetalum, and was at 
first represented by carterensis, the latter being a twilight species, which gave origin to the 
cavernarum. We regard this series as the best and clearest proof of the derivative theory which 
we have observed, proof so clear as to amount almost to a demonstration of species- and genus¬ 
making by a change in the environment. 
Iu Mr. Hubbard’s collection from Wyandotte Cave (Aug.,'1885) I found a single carterensis considerably larger 
than any from the Carter Caves, but the body and tips of the anteun® are perhaps a shade paler. The eyes are 
normal, black, while the two last joints of the anteun® are a little slenderer than in my types of var. carterensis, but 
the last joint is decidedly shorter than in the form cavernarum-, the specimen is much larger than any P. cavernarum 
from Wyandotte Cave. 
Genus Scoterpes Cope. 
Spirostreplion (Pseudotremia) Pack., Amer. Naturalist, v, 748, December, 1871. 
Scoterpes Cope, Amer. Naturalist, vi, p. 409, 414, July, 1872. 
Scoterpes PacV, Proc. Aiaer. Phil. Soc. Phila., xxi, 192, 1883. 
Body very long and slender, not fusiform; consisting of thirty segments besides the head, and with about fifty- 
two pairs of legs, with the penultimate joint very long. Head rather large and unusually broad; no eyes present; 
the gen® unusually large, extending high up on the vertex, but not so globose as in Trickopetalum ; the front is also 
carried farther up on the vertex than usual, and is much broader than long; the clypeus flat, slightly bilobed on the 
front edge. The antenn® are moderately long and hairy, with the sixth segment scarcely longer than in Trichope- 
talum, but more uniform in thickness, scarcely longer than thick; the terminal joint as long as the sixth, the end 
conical, more produced than in Trichopetalum or Zygonopus; at the tip are four rather long sense-set®. Body seg¬ 
ments becoming, as usual, smaller next to the head; the anterior of each division of the arthromere much swollen 
high up on the sides; each shoulder with three tubercles, which are arranged in a scalene triangle and bear much 
longer set® than in the other genera, though not quite so long as the body is thick. The legs are long and slender, 
much more so than in Trichopetalum, and somewhat more so than in Zygonopus. In the male the eighth pair of legs 
are rudimentary, being two-jointed, the second joint only one-fourth longer than the basal, and ending in a well- 
developed stout claw. The genital armature minute and very rudimentary, pale, scarcely chitiuous ; the outer lamina 
short and thick, with a stout external recurved spine, and two terminal obtuse points; the inner lamina shorter 
