48 G. O. Sara. 



Gen. Alona, Baird. 



Remarks. — I am not prepared to agree with Prof. 

 Lilljeborg in changing the name Alona to Lynceus. If the 

 latter name is to be used, it should in my opinion more pro- 

 perly be applied to another group of Lynceidæ, viz., that 

 comprised in the genus Chydorus Baird, of which one of the 

 species, C. sphæricus Muller, is by far the commonest of all 

 Lynceidæ, whereas Alona quadr angularis Müller, which is 

 regarded by Prof. Lilljeborg as the type of the family, is 

 rather local in its occurrence. 



The species of this genus are easily recognizable by 

 the oval quadrangular shape of the carapace, which in most 

 cases exhibits a rather regular longitudinal striation, though 

 in some few species this sculpture is indistinct or wholly 

 wanting. 



Numerous species of this genus have been described 

 from all parts of the world; but in some cases, forms have 

 been referred to it, which in my opinion belong to other 

 Lynceid genera. About 7 species have hitherto been re- 

 corded from South America, 2 of them however, A. Millleri 

 Richard and A. Davidi Richard, not belonging to this genus 

 but to the next. I have myself observed in my aquaria 9 

 different species, which will be treated of below. 



18. Alona af finis, Ley dig. 



(PL IX, figs. 1, a— d). 



Lynceus afflnis, Leydig, Naturgeschichte der Daphinden* p. 223, Pl. 



IX, figs. 68, 69. 

 Syn. Lynceus quadrangularis Fischer (not Muller). 

 » Alona oblonga, P. E. Muller. 



