ENTOMOSTRACA OF MINNESOTA. 237 



*Duiilieveclia setiger Birge. 



Plate LXIV, Fig. 3 



Leugth 0.4 mm. to 0..5 mm. Minnesota specimens measured 0.5 

 mm. Tliis species is but rarely encountered, and is so peculiar as to 

 be easily recognized when seen. Alona intermedia has a post-abdomen 

 with clusters of bristles, but in Dunhevldia the post-abdomen is more 

 as in species of Gmptoleberis than any other genus. The markings 

 upon the shell are very indistinct. Birge says that the male is ^limi- 

 lar in form to the female. The first foot has a stout hook. The claws 

 are smooth in both sexes. This species has been found by Daday in 

 Hungary. 



GENUS LYNCEUS O. F. Midler. 



The perplexing inter-relations between the three genera Alona, 

 AloneUa and Plenroxus give rise to the utmost confusion. No two 

 authors are agreed as to their respective limits, and the points given 

 by Kurz, who has carefully gone over the ground, are obviously in- 

 sufficient. Although there may be practical benefits to be derived 

 from the continuance of the nomenclature in use for groups which 

 in the general view can be distinguished, the value from a theoretical 

 standpoint is reduced to a minimum. 



The genus Camptocercus (including here Acroperus, which differs 

 solely in the form of the abdomen, as a sub-genus) passes through 

 Alonopsi)^ into the group represented by Alona. Leydigia, although 

 very near such forms as Alona qnadrangidaris, may be conveniently 

 distinguished as a transition to species like Ihjocn/ptiai. 



Phriu'ura, GraptoleberiH and 7>(o//((^yjV//r(, each containing few species 

 which can be readily recognized, fill a place in the system; but it is 

 practically impossible to distinguish Alona from Fleuroxns without in- 

 stituting the very indefinite genus AloneUa to contain a variety of 

 small intermediate forms. Percanlha, Bhypophllus, Ha iporhynchus and 

 PleiDv.rxs seem to be pretty generally regarded as constituting a single 

 group which may be recognized by the long rostrum, high shell and 

 greater development of the antenna bristles. Alona, on the other 

 hand, with its broader fornices, shorter beak, fairly developed an- 

 tennte, and more rectangular shell, is, perhaps, the pivotal point of 

 the group. According to this view, then, the old name Lyneeti.s is re- 

 vived for the aggregate; and the other names are retained, in pari, 

 as titles of largely conventional groups or sub genera, thus: 



