Fresh- water Entomostraca of South America. 37 



duced than in that species. Colour greyish white. Length 

 of adult female 0.40 mm. 



Remarks. — This form at first sight looks very like 

 the European species M. laticomis (Jurine), and may, indeed, 

 have been mistaken for it by other authors. On a closer 

 examination, however, some well-marked differences may be 

 found to exist, which seem to forbid an identification of the 

 2 forms with one another. Thus the peculiar jagged appear- 

 ance of the upper edge of the carapace is very different from 

 the fine serration of this edge in M. laticomis, and is in 

 reality caused by the projecting scale-like ridges with which 

 the whole upper surface of the shell is sculptured. These 

 scales are well seen even in the cephalic shield (see figs. 10, 11), 

 and are, indeed, more conspicuous than in any other species 

 with which jl am aquainted; hence the specific name here 

 proposed. The antennulæ also are of somewhat different 

 form, and the epipodites of the 1st and last pairs of legs 

 (see fig. 12) are more fully developed. 



Biological Observations. — This form was 

 only observed in 2 of my aquaria, though rather plenti- 

 fully in these. The specimens generally kept near the 

 bottom, and moved about in a jumping manner similar 

 to that of the preceding species, though with considerably 

 less speed. Male specimens I did not succeed in finding, 

 and cannot of course state, whether there are any differ- 

 ences between the secondary sexual characters of this species 

 and those of M. laticomis. 



Occurrence. — The 2 aquaria in which this form 

 appeared, were both prepared with mud from Itatiba. 



