Fresh -water Entomostraca of South America. 55 



the caudal part, as also in the presence of a distinet denti- 

 form projection on each valve at the infero-posteal corner, 

 this latter character having given rise to the specific name 

 here proposed. 



Biological Observations. — In some of my 

 aquaria, this form proved to be present in considerable 

 abundance, though its small size rendered it rather difficult 

 to detect while still in the aquarium. It was chiefly by the 

 aid of the dipping-tube that I succeeded in securing speci- 

 mens of it. In the small quantities of mud taken up from 

 the bottom of the aquaria by this means, and placed in a 

 shallow watch-glass for observation, I was almost sure to 

 find some specimens of this form, and they were not diffi- 

 cult to detect with a strong magnifying-glass, as, like most 

 other Lynceidæ, they congregated after some time on the 

 lighter side of the watch-glass. The swimming movements 

 of the animal resemble those of most other Alonœ, consist- 

 ing in a rather slow and somewhat tremulous dart through 

 the water, caused by rapid strokes of the antennæ. Though 

 several ephippial females were observed, I did not succeed 

 in getting any male specimen. 



Occurrence. — The aquaria in which this form 

 occurred, were prepared with mud, partly from the neigh- 

 bourhood of Sâo Paulo, partly from Ipiranga. 



24. Alona glabra, n. sp. 



PI. IX, figs. 6, 6 a). 



Specific Characters. — Female. Carapace, 



seen laterally, oblong quadrangular in form, dorsal margin 



evenly arched, ventral almost straight, hind edge slightly 



curved, with the upper corner obtuse, the lower rounded off 



