1048 Wisconsin Academy of Sciences , Arts, and Letters. 
has no strong foot in the female; the terminal claw has no- 
secondary denticle in the middle. Still other features are 
wanting if 0. tenuicaudis is also drawn into comparison. If 
these species are to be placed in Euryalona there are left 
practically no characters to separate that genus from Alona. 
This is another of those cases, numerous in this region of 
the Chydorina, where it is hard to determine the generic posi¬ 
tion of a species, not because of our ignorance so much as be¬ 
cause of the close and conflicting inter-relationships of specie^ 
The new form cannot be placed in Alona, nor can it be sep¬ 
arated from A. tenuicaudis , and I see no other solution hut to 
make a new genus for the two species. It is possible that a 
reviser of the group might prefer to make this a sub-genus; 
but I believe it is as well distinguished as several other genera 
of Chydorina. 
This species is not included in my list of species, referred 
to in the first paragraph of this paper; and in the same list 0. 
tenuicaudis is placed under Alona. When that list was pre¬ 
pared I had not carefully studied all of my southern material. 
6. Note on the Genus Alonella. 
The genus Alonella was proposed by G. O. Sars in T861 
(’62, p. 288) for the form described by him a little earlier 
in the year as Alona pygmaea and which had been still earlier 
described by Baird as Acroperus nanus. To the same genus 
Sars assigned Lynceus rostratus Koch and L. excisus Fischer; 
to these L. exiguus Lilljeborg must necessarily he added. The 
judgment of later writers has varied with respect to the genus 
thus established. Kurz (’73) accepts it in full. P. E. Muel¬ 
ler (’67), Hellich (’77), Daday (’88) place A. rostrata in 
the genus Alona and the rest in Pleuroxus. Lilljeborg (’00) 
places A. rostrata in his genus Lynceus {—Alona), although 
with doubt, and the others in Alonella as also does Stenroos 
(’95). Stingelin (’04) places A. excisa in Alonella and Daday 
(’05) does the same thing. In 1888 Sars added to the genus 
two species originally described by King as belonging to Aloria. 
These were A. Jcarua and diaphnnaj constituting a very dis- 
