STATE GEOLOGIST. 95 



Sp. 2. Alona angulata, Birge. 



Dorsal margin considerably arched, terminating in a more or 

 less obvious angle at the hinder corner; the hinder edge is convex, 

 as is also the front margin; the ventral margin bears plumose setas. 

 Beak pointed, extending nearly to level of ventral margin of the 

 valves. Fornices broad. Shell obviously striated diagonally and 

 less obviously marked by cross lines. Post-abdom 3n broad, trun- 

 cate; about twelve anal teeth, with a series of scales and hairs back 

 of them. The pigment fleck is much smaller than the eye. Male 

 smaller; beak shorter; post-abdomen with a lateral row of hairs; 

 anterior feet hooked; sculpture less distinct. [Birge.] Length of 

 female 0.4 mm; male 0.35 mm. 



Sp. 3. Alona sangruinea, P. E. Mueller. 



(Plate I. Fig. 20.) 



Body nearly rectangular; ventral margin nearly straight, with 

 short setas; posterior angle rounded, unarmed. Beak short; pig- 

 ment fleck much larger than the eye. Post-abdomen large, the 

 end truncate, broadened; posterior margin rounded, with a series 

 of spines and a lateral row of scales; terminal claw with a small 

 spine. The shell is ornamented with fine, close, longitudinal 

 striations. Length 0.9 mm. Alona elegans is very near to this 

 and should have followed. In August, 1878, I took an Alona 

 marked as in A. sanguinea and agreeing with Mueller's description 

 in all points which can be verified in the drawing. The small size 

 of the eye is remarkable for so large an animal. I have never again 

 seen this species; it seems to be very rare here and in Europe. 



Sp. 4. Alona tenuicaudis, Sars. 



(Plate I. Fi^. 11.) 



Alona tenuicaudis, sars, p. b. muelleb, kubz. 

 Alona camptocercoides, schobdlee. 



Form nearly rectangular; ventral margin rounded, with long 

 setae, posterior angle rounded. Beak short, pigment fleck smaller 

 than the eye. Post-abdomen with sides parallel, long, incised 

 below; lower angle armed with about six strong teeth, remainder 

 of the series small; a lateral line of scales present; claws with a 

 strong basal spine. The shell is striate with longitudinal lines. 

 Length 0.5 mm. 



One of the most easily recognized species; not identified in 

 America. 



