ENTOMOSTRACA OF MINNESOTA. 231 
the last, but it is not certain that the beak is cleft, although it has a 
peculiar form (not indicated in the figure) near the end. The length 
is 0.7 mm. The terminal sete of the antennules are very unequal; 
but in most points, as in the armature of the post-abdomen, the details 
resemble ©. macrurus. [This is probably but a variety. ] 
GENUS ALONOPSIS Sars. 
This curious genus includes three species of small Lynceids which 
exhibit a combination of characters. The form of the beak and head 
is like that of Plewroxus, which the form and sculpture of the shell 
otherwise resembles. The back is extended more or less in a knife- 
like ridge above, thus resembling Acroperus, a resemblance heightened 
by the excavated lower margin. The form of the post-abdomen 
approaches that of Acroperus, but in that genus it is of about equal 
width throughout and in this it rapidly narrows. The internal organs 
and feet are of the typical lynceid form, while the antenne are as in 
Pleuroxus. . 
The type of the genus, A. elongata, is apparently much closer to 
Acroperus than the two species which have been identified in America. 
Shell sub rectangular, high, produced into a ridge above; lower 
margin convex anteriorly, concave behind; beak rather long; anten- 
nules slender; antennz with eight sete; abdomen long, narrowed 
toward end, incised at the extremity; claw rather large, with median 
spines and a basal thorn; third foot with a long bristle. Male smaller, 
without the carina above; orifice of sexual organs in front of the claw, 
which is removed from the anterior margin. The young are more 
elongate and (sometimes) have hexagonal reticulations instead of the 
usual strong diagonal strie. Motion slow. 
Alonopsis elongata Sars. 
Lynceus macrurus—Lievin, Zenker, Leydig. 
Alono elongata—Sars. 
Acroperus intermedius—Schoedler. 
The shell is wide, the upper margin forming an even curve, mani- 
festly angled behind; ventral margin nearly straight, ciliated through- 
out, with a single tooth behind. Fornices large; head narrow, not 
earinate. Post-abdomen compressed, truncate at the end, armed with 
a Series of marginal spines and of lateral scales; caudal claws large, 
with a single spine at the base and two median spines followed by a 
series of minute sete. 
This form I have never seen, and it seems somewhat doubtful that 
the following really belongs with it. 
