(10) 



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 mtermedius, 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 length, 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 tho7-acic segment is narrowed anteriorly, showing the 

 epimera, but is not emarginate. The others are distinctly emarginate on 

 the sides, the eraarginations 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 



