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tLe rami and three-fifths as wide as long. The second joint of the outer 
ramus is ovate and twice the length of the first. The inner ramus reaches 
to the middle of this joint, is broader than in A. communis , but of similar 
shape, and indistinctly bifid at tip. 
The opercular 'plates do not reach the tip of the abdomen, but are 
obliquely truncate, their posterior margins forming a wide re-entering angle. 
The anal stylets are very short, flat and broad. The peduncle is ob-tri- 
angular, nearly as broad as long, the tip oblique, the inner*edge being the 
longer and somewhat rounded. The outer ramus is narrow-ovate, obtuse, 
as long as the peduncle, and seven-eighths the length of the outer ramus. 
This is also ovate and obtuse, the outer margin nearly straight, the inner 
convex. All the joints bear many marginal spines, longest at tips of rami. 
This species was found in clear, rocky rills in Jackson and Union 
counties in Southern Illinois. 
Asellus intermedius , Forbes. This species is more closely allied to A 
communis than to A. brevicauda, but, as will be seen from the description, 
stands between these two. Its lengthy in adult females, is but 6 mm., its 
breadth about 2 mm. The sides of the head diverge posteriorly, and the 
lateral lobe is smaller than in brevicauda , bearing a single spine and a few 
short hairs. The first thoracic segment is narrowed anteriorly, showing the 
epimera, but is not emarginate. The others are distinctly emarginate on 
the sides, the emarginations moving gradually backwards, in the succeeding 
segments, from the anterior to the posterior angles. The free margins of 
all the segments are strongly spined. The lobe of the hind margin of the 
abdomen is shorter and broader than in brevicauda , reaching laterally to the 
middle of base of each caudal stylet, and extending backward to the middle 
of length of pedicel. The posterior angles of the abdomen are regularly 
rounded and indistinct. 
The flagellum of the upper antenna is nine-jointed, the first joint short, 
about half as long as fourth. 
The first pair of feet of the male are stout, the hand two-thirds as wide 
as long, the palmar margin straight, with a slender tooth at base and a strong 
conical one at middle. The posterior margin of the propodus is very short, 
about one-sixth the palmar, the dactyl long and strong, the tip of the claw 
when closed reaching beyond the base of the hand. The posterior margin 
of the dactyl is serrate with appressed teeth as in brevicauda. The carpus 
is triangular, the posterior margin straight and usually armed with a strong 
blunt spine at its distal fifth. The hand of the female is narrower 
and smaller, its breadth being about half its length. The palm is straight 
and shorter than in the male, the posterior margin longer, (nearly half 
the palmar), the two margins forming a wide angle. The spine at this 
angle is slender, and there is no trace of a tooth on the palmar margin, 
or on the carpus. 
The first pair of genital plates in the male are short and broad, the 
basal joint scarcely longer than wide, the second joint elliptical, broadly 
rounded at tip and convex both sides, fringed posteriorly and on pos- 
terior half of outer margin by a few short hairs. The pedicel of the 
