1050 Wisconsin Academy of Sciences, Arts-, and Letters. 
b. Paralonella. Rostrum short, hardly exceeding anten- 
nules. Post abdomen with very small marginal denticles, 
usually with, but rarely without, lateral fascicles, which if 
present ar© larger than the marginals; claws with one basal 
spine. A. karua (King) ; A. diapkana (King) ; A. dentifera 
Sars; A. globulosa Daday; ( —sculpta Sars) ; A. Imeolata Sars. 
Related to these, but with better developed postabdominal den- 
tices is A. punctata Daday, whose striation recalls A. nana. In 
general form these approach Alona. 
c. Pleuroxalonella. Rostrum exceeding antennules but not 
recurved. Postabdomen with marginal denticles only; claws 
with two basal spines. General form of body and postabdo¬ 
men Pleuroxus-like. A. excisa (Koch) ; A. exigua Lilljeborg; 
A. cklathratula Sars; A. breviceps Stingelin. 
There remains one species which does not fit into any of 
these subgenera: A. nitidula Sars. In general form this 
closely resembles a Ckyidorus of the barroisi group; but the 
postabdomen is quite different and of the Alonella type. 
I do not offer this arrangement as satisfactory, yet I can 
see nothing better at present. Some might prefer to make 
independent genera instead of subgenera out of these .three 
groups. But the interrelations of the various species are so 
close that I see little or no advantage in so doing, at any rate 
until the whole family is carefully revised; when this is done 
the systematic arrangement is pretty sure to be changed from 
that here indicated or from any as yet proposed. 
All students of the Cladocera know that the genera of the 
Chydorina are very unsatisfactory. This has always been 
true, and as the number of known species increases the dis¬ 
satisfaction becomes more acute. Two policies have been tried 
in order to better things: By one, a large section of the 
family was included in one genus, with numerous subgenera. 
This was tried by Herrick ( ? 84), who united under Lynceus 
the genera Alona, Alonella, and Pleuroxus. If the plan were 
tried again Ckyidorus (which Herrick doubtfully separated) 
would have to be included, as the barroisi forms connect im¬ 
mediately with Pleuroxus. This plan has been before stu¬ 
dents for twenty-five years and no one has followed it; so it 
