38 
MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 
flagellum is usually a little shorter. The propodus of the first pair of feet is similar in outline, but 
the palmar margin and dactyl are shorter, and the posterior margin longer. The second pair is 
extremely like the second of the male, but is decidedly smaller than the first. The telson affords 
a difference so remarkable, that the two sexes, at first sight, would hardly be referred to the same 
genus. In the female this is very similar to the telson of C. gracilis Smith. It is flattened and 
slightly etnarginate, a little longer than broad, extending to the tips of the second pair of anal 
legs, and bears two terminal clusters of spines of four or five each. 
This species was first discovered by me in a well at Normal, Illinois, during the summer of 
1875. It was subsequently found by Mr. Harry Harman in great numbers in springs, and even 
at the mouths of drains, after a long period of heavy rains. With the advent of dry weather it 
entirely disappeared from these, but still occurs sparingly in wells. (S. A. Forbes.) 
Ceangonyx lucifttgus Hay. 
Crangonyx lucifugus Hay, Arner. Naturalist, xvi., 144-5. 1882. 
The following description is copied from Mr. Hay: 
This is a small, rather elongated species, that was obtained from a well in Abingdon, Knox county, Illinois. As 
befits its subterranean mode of life, it is blind, and of a pale color. In length the largest specimens measure about 6 mm . 
Male. —Antennal® scarcely one-haif as long as the body. The third segment of the peduncle two-thirds as long 
as the second; this, two-thirds the length of the first. Flagellum consisting of about 14 segments. The secondary 
flagellum very short, and with but 2 segments. Antenn® short, only half as long as the antennul®. Last 2 segments 
of its peduncle elongated. Flagellum consisting of but about 5 segments, and shorter than the last two segments of 
the peduncle taken together. 
Second pair of thoracic legs stouter than the first. Propodite of first pair quadrate, with nearly a right angle 
between the palmar and posterior margins. Palmar surface on each side of the cutting edge, with a row of about 6 
notched and ciliated spines, one or two of which at the posterior angle are larger than the others. The cutting edge 
is entire. Dactylopodite as long as the palmar margin, and furnished along the concave edge with a few hairs. 
Propodite of the second pair of legs ovate in outline, twice as long as broad. The palmar margin curving grad¬ 
ually into the posterior margin. The cutting edge of the palmar surface uneven, and having, near the insertion of 
the dactyl, a square projection. The palmar surface also armed with two rows of notched and ciliated spines, five 
in the inner row, seven in the outer. Dactyl short and stout. 
Two posterior pairs of thoracic legs longest of all and about equal to each other. All the legs are stout and 
their basal segments squamiform. 
P ostero-lateral angle of first ab dominal segment rounded; of second and third, from obtuse-angled to right-angled. 
First pair of caudal stylets extending a little farther back than the second; these slightly exceeding the third. 
The peduncle of the first pair somewhat curved, w ith the concavity above, the rami equal and two-thirds as long as 
the peduncle. The peduncle of the second pair little longer than the outer ramus. Inner ramus nearly twice as long 
as the outer. Third pair of caudal stylets rudimentary, consisting of but a single segment. This somewhat longer 
than the telson, broadly ovate, two-thirds as broad as long, and furnished at the tip with two short spines. 
Telson a little longer than wide, narrowing a little to the truncated tip, which is provided at each postero¬ 
lateral angle with a couple of stout spines. 
Female. —In the female the propodite of the anterior pair of feet resembles closely that of the corresponding 
foot of the male. The palmar margin of the second propodite is less oblique than in the second foot of the male, and 
does not pass so gradually into the posterior margin. It is also destitute of the jagged edge and the square process 
of the male foot. There are fewer spines along the margin. O ne of the spines at the posterior angle is very long 
and stout. 
This species appears to resemble G. tenuis Smith, but is evidently different. In that species, as described by 
Prof. S. I. Smith, the first pair of feet is stouter than the second, and has the palmar margin of the propodite much 
more oblique. The reverse is true of the species I describe. Nor do I understand from the description of C. tenuis 
that the posterior caudal stylets each consist of a single segment. There are some minor differences. From C. vitreus, 
judging from Professor Cope’s description in American Naturalist, volume vi., page 422, it must differ in the caudai 
stylets. “ Penultimate segment with a stout limb, with two equal styles,” is a statement that will not apply to my 
species, whichever the “penultimate” segment may be. 
Cambaeus pellucidus (Tellkampf). 
Astacuspellucidus Tellkampf, Arch. f. Anat., Phys. u. Wissensch. Med'., 383, 1844. 
Gambarus pellucidus Erichson, Archiv f. Naturgesch., xii, Jahrg. I, 95, 1846. 
Orconectes pellucidus Cope, and Orconectes inermis Cope, Amer. Naturalist, vi, 410, 419, 1872. 
Cambarus pellucidus Smith, Eep. U. S. Com. Fish., 1872 and 1873, 639, 1874. 
Cambaruspellucidus Faxon, Proc. Amer. Acad. Arts and Sci., xx, 139, 1884; revision, 90, 1885. 
Next to the blind-fish of Mammoth anil other caves, the blind crayfish first discovered in 1842 
by Dr. W. T. Craige has, from its size, attracted the most general attention from the public. We 
