134 



somewhat obliquely rounded, posterior scarcely narrower and obtuse at the 

 lower corner; seen dorsally, oblong oval in outline, slightly constricted in 

 front of the middle, greatest width behind and not attaining half the length, 

 both extremites obtusely pointed, the anterior narrower than the posterior. 

 Surface of shell of a somewhat dull appearance, and clothed with short hairs. 

 Natatory setae of posterior antennae extremely rudimentary and easily over- 

 looked, apical claws rather strong and coarsely denticulated. Spines on outer- 

 most masticatory lobe of the maxillae armed with 2 strong denticles on each 

 side of the terminal part. Caudal rami comparatively strong and quite straight, 

 with the dorsal edge minutely spinulose, apical claws remarkably stout, the 

 distal one not nearly attaining half the length of the ramus, dorsal bristle 

 replaced by a thickish spine somewhat similar to the apical claws, but much 

 shorter. 



Colour uniformly dark olivaceous green. 



Length of adult female 1.25 mm. 



Male unknown. 



Remarks. The reference of this form to the Australian genus Ilyodromns 

 G. O. Sars, proposed by Brady and Norman, and also sanctioned by Kauf- 

 mann, seems to me to be quite inadmissible, and is in reality only founded on 

 the somewhat similar transformation of the dorsal bristle on the caudal rami. 

 In other respects this genus diffejs very conspicuously both as to the structure 

 of the shell and to that of some of the appendages. On the other hand, 

 apart from the above-named particularity, I find that the agreement of the 

 present species with the preceding ones is quite unmistacable. 



Occurrence. I have hitherto only met with this form in a single place, 

 viz., in a shallow ditch near Christiania. The animal is rather sluggish, and 

 keep constantly at the bottom. 



Distribution. British Isles, Hungary, Bohemia, Switze r land. 



Group 7. Cypridopsides. 



Remarks. The forms referable to this group are in particular distinguished 

 from the other fresh water Cypridae by the rudimentary condition of the caudal 

 rami. True, in 2 of the genera, Cypretta Vavra and Paracypretta G. O. Sars, 

 the reduction of these rami appears somewhat less complete than in the other 

 genera; but also in this case the reduction is great ennough to distinguish 

 them from the more typical Cypridae. Several genera have been established 



