100 TWELFTH AKl^UAL REPORT. 



Sp. 15. Alona parvula, Kurz. 



The body is sub-quadrangular, arched above; ventral margin 

 straight, rounded behind. Shell marked by longitudinal, feeble 

 and irregular lines. The post-abdomen is narrower toward the end, 

 with eight or more teeth; the row of scales is absent; at the end it 

 is sharply truncate and incised; the claws have short basal spines.. 

 Hardly to be distinguished from the next. 



(18 ) Alona parvula, var. tuberculata, Kurz. 



Alona tuherculata, kurz. 

 Alona verrucosa, lutz. 



The species described by Kurz in 1874, and more at length by 

 Lutz under a different name in 1878, appears to be simply a tuber- 

 culate variety of the above. Observations upon the American re- 

 presentatives of the two forms indicate a close relationship between 

 them. The shell is covered with rows of tubercles (or depressions?) 

 which vary in number greatly. 



Sp. 16. Alona glacialis, Birge. 



(Plate G. Figs. 2, 3 and 8.) 



I do not know how to distinguish this certainly from A. par- 

 vula. It, however, seems to have the lower angle of the post-abdo- 

 men less squarely truncate and the incision less obvious. Birge 

 says that the abdomen is rounded. I have found specimens which 

 apparently belong here, with the post-abdomen rather sharply 

 angled and deeply incised; there were about fourteen teeth with a 

 row of hairs in front. The form is hardly to be distinguished from 

 another variety which has a shorter post-abdomen, rounded below^ 

 and with only about seven or eight teeth and with a smooth shell. 

 This form passes directly into a tuberculate variety, having the 

 post-abdomen similar bat the shell covered with numerous rows of 

 tubercles. Sometimes a transition from a lined shell to a tuber- 

 culate shell is seen (as in plate G, fig. 14). Alona tuberculata, Kurzr 

 is said to have a truncate and incised post-abdomen with no lateral 

 row of hairs, Birge thinks these identical; if so, our form referred 

 to A. glacialis is identical with A. parvula. There is also a form 

 found with the above in which no markings are visible and the 

 shell is considerably arched; these were, however, nearly all ephip- 

 pial females or approaching that period. 



