Fresh-water Entomostraca of South America. 31 



At the close of the season the ephippial formation was ap- 

 parent in the greater number of the females, and detached 

 ephippia (fig. 11) were often taken up from the bottom by 

 the aid of the dipping- tube. At the same time also male 

 specimens' not unfrequently appeared ; but they long escaped 

 my attention on account of their great resemblance to young 

 females (see fig. 12). Indeed, the secondary sexual charac- 

 ters are far less pronounced in this form than in most other 

 Macrothricidæ, and it is only on a close examination that it 

 can be proved, that a slight transformation has taken place 

 in the structure of the antennulæ (fig. 13) and the 1st pair 

 of legs (fig. 14). The caudal part, on the other hand, is 

 of quite the same appearance as in the female. 



Occurrence. — The aquaria in which this form ap- 

 peared, were all prepared with mud from the neighbourhood 

 of Sâo Paulo. 



Distribution. — The specimens examined by Mr. .Rich- 

 ard were found in a bottom-sample taken from some swamp 

 in the French dominion of Congo. Mr. Daday has recently 

 recorded the same form also from the German dominion of 

 New Guinea. The occurrence of this and other forms on 

 both sides of the Atlantic, at nearly the same latitude, is 

 very remarkable, and cannot be accounted for by the accidental 

 transport of resting ova by the aid of birds, since no regular 

 migration of birds is known to take place across the Atlantic. 



Gen. Iheringula, G. O. Sars. 

 10. Iheringula paulensis, G. O. Sars. 



Remarks. — A detailled description of this interest- 

 ing form with numerous figures, has been given by the pre- 



