56 G. 0. Sårs. 



and unarmed. Head of about the same appearance as in the 

 preceding species. Surface of shell perfectly smooth, without 

 any trace of striæ. Ocellus somewhat smaller than tbe 

 eye, and placed almost midway between it and the tip of 

 the rostrum. Lip-plate with the lower edge evenly curved. 

 Caudal part of moderate size and almost uniform width, 

 dorsal edge below the anal orifice scarcely curved at all, 

 supra-anal projection well-marked and located considerably 

 above the middle, lower corner rectangular, denticles of the 

 marginal rows very unequal, the 3 distal ones on each side 

 being much larger than the others, those of the lateral rows 

 extremely delicate, about 7 on each side; caudal claws with 

 a denticle of moderate size at the base. Body very pellucid 

 and almost colourless. Length of adult female 0.38 mm. 



Remarks. — The species to which this form exhibits 

 the nearest relationship, is that described by the present 

 author from Australia as A. Icevissima, in which the surface 

 of the shell is also perfectly smooth. It differs, however, in 

 a somewhat different form and armature of the caudal part, 

 as also in size and colour. 



Occurrence. — I only found this form in one of 

 my aquaria, but there in great abundance. This aquarium 

 was prepared with mud from Argentina. 



25. Alona verrucosa, n. sp. 



(PI. IX, figs. 1, 7 a). 

 Specific Characters. — Female. Carapace, 

 seen laterally, rather short and broad, rounded quadrangular 

 in form, height almost equalling the length, posterior ex- 

 tremity almost transversely truncated, with the upper corner 

 distinct, the lower rounded off. Head about as in the 2 



