Hydrachnellae 



305 



spine on the distal, inner margin. The coxal plates lie in four groups of 

 two each but are also united with one another and to the ventral shield. 

 The anterior coxal plate group has a more or less long, posteriorly 

 directed, subcutaneous process which often reaches to the posterior 

 coxal plates. Posterior plates, especially iv, as a rule are rectangular 

 and large. Legs i or legs i and ii are 

 often thickened and often have 

 paired, swordlike setae on protuber- 

 ances. Usually the legs have swim- 

 ming hairs. The genital organ has a 

 weak-skinned form with two geni- 

 tal plates; females of certain genera 

 have four plates and have not under 

 five or six pairs and often more 

 genital suckers (the suckers seldom 

 lie free in the skin). The genital 

 organ of the armored forms has 

 two or more weakly differentiated ^. ,,o xr • t j 



•^ Figure 238 Neumania ciirvipes Lund- 



genital plates and many suckers. blad. Venter. (After Lundblad 1930) 



Unionicolinae Koenike, 1909 



Genera and subgenera: 



1. Unionicola Haldeman, 1842 



a. Unionicola s. str. 



Type. Acarus ypsilophorus Bonz, 1783 



b. Atax Koch, 1842 (= Hexatax Thor, 1926) 

 Type. Hydrachna crassipes Miiller, 1776 



c. Pentatax Thox, 1926 



Type. Atax bonzi Claparede, 1868 



d. PolyataxWiQis, 1933 



Type. Poly atax japonicus Viets, 1933 



e. Unionicolides Lundblad, 1937 



Type. Unionicola {Unionicolides) 5/cfl Lundblad, 



2. ^race//« Lundblad, 1937 



a. A tacella s. str. 



Type. Atacella clathrata Lundblad, 1937 



b. Atacellidesl^ux\dh\?id, 1941 

 Type. Atax rugosus Koenike, 1890 



3. Polyatacides Lundblad, 1941 



Type. Unionicola prominens Koenike, 1914 



1937 



