Fresh-water Entomostraca of South America. 45 



as usual, much smaller than female, with the dorsal margin 

 of the carapace less arched and the rostral projection very 

 much shorter. Colour of female reddish orange, sometimes 

 changing to bright blood-red. Length of adult female 0.85 

 mm., of male 0.62 mm. 



Remarks. — This is a very distinct and easily re- 

 cognizable form, especially remarkable for the peculiar de- 

 velopment of the rostral projection. It is only in females, 

 however, that this projection attains its full development; in 

 male specimens (see fig. 10) it is always very much shorter. 

 The very large and broad caudal part (fig. 4) somewhat re- 

 sembles that in the species of the genus Leydigia; but its 

 armature is rather different, and agrees better with that in 

 the genus Mona. 



Biological Observations. — This pretty form 

 was found in several of my aquaria, and in some of them 

 was rather plentiful. It was not easy to observe the indivi- 

 duals, however, while still in the aquarium, as they generally, 

 like most other Lynceidæ, kept themselves more or less 

 deeply buried in the loose mud on the bottom, or concealed 

 among the aquatic plants, only rarely making a short swim- 

 ming excursion through the water or attaching themselves 

 to the walls of the aquarium. To catch this form, an 

 ordinary dipping-tube was used, by the aid of which small 

 quantities of the bottom-material were taken up, and placed 

 in a shallow watch-glass for observation, when the speci- 

 mens very soon became apparent, swimming out from the 

 mud towards the lighter side of the watch-glass. They could 

 then be immediately selected, being easily recognizable, even 

 with the naked eye, from the other Lynceids occurring in 

 the aquarium, both by their comparatively large size and 

 their bright red colour. 



