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 setse of the antennules are very unequal; 

 but in most points, as in the armature of the post-abdomen, the details 

 resemble G. 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 Pleuroxm, 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 antennie are as in 

 Fleu7'oxus. 



The type of the genus, A. elongafa, 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; antennae with eight setai; 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 strise. Motion slow. 



Alonopsis elongata Sars. 



Lynceus macrurus — Lievin, Zenker, Leydig. 



Alono elongata — Sars. 



Acroperus intermedius — Schoed ler. 



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 

 cariuate. 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 setiB. 



This form I have never seen, and it seems somewhat doubtful that 

 the following really belongs with it. 



