schaeffer: donaciini of the new world. 57 
absent in one or both sexes of a few species ; third antennal 
joint generally shorter than fourth ; "• vaginal plates of 
female unequal, the lower plate longer than the upper and 
generally triangularly converging towards apex into a more 
or less acute point with the outer edges uneven or serrate ^. subg. Plalenmaris. 
Subgenus Donacia Fab. 
Key to males. ^ 
1. Posterior tibiae internally serrate and at apex produced into a 
moderately long, tooth-like projection; posterior femora 
extending below the apices of elytra, strongly bent a little 
below base and thence very strongly incrassate, armed below 
with two teeth and behind the posterior tooth a serrate ridge, 
which is often reduced to one or more denticles (plate V, 
fig. 4) militaris Lac. 
Posterior tibiae at apex simple, not produced into a tooth- 
like process 2. 
2. First joint of anterior tarsi broadly dilated, subcordate; 
posterior femora with a large, somewhat compressed tri- 
angular tooth and a more or less distinct denticle in front of 
the latter palmata Oliv. 
First joint of anterior tarsi normal, not subcordate 3. 
3. Middle tibiae at apex internally produced into a short, but 
distinct tooth; posterior femora with a large, somewhat 
compressed triangular tooth and a more or less distinct 
denticle in front of the latter (plate V, fig. i.) piscatrix Lac. 
Middle tibiae not produced at apex into a tooth 4. 
4. Hind femora long, extending to or beyond elytral apices .... 5. 
Hind femora decidedly shorter, extending never to the elytral 
apices 11. 
5. Posterior femora armed with two teeth and with a serrate 
ridge behind the posterior tooth which is often reduced to 
one or more denticles; the small anterior tooth occasionally 
very feeble or absent ; prothorax shining, except in caerM/ea 8. 
Posterior femora armed with a single tooth; prothorax dull, 
alutaceous, in rufescens generally more or less shining 6. 
6. Posterior femora reaching to elytral apices, small species, 
color flavous with or without golden tint; antennae narrowly 
annulated with black; femora above with a more or less 
distinct dark space rufescens Lac. 
•* The third antennal joint of the male of the European consimilis is longer than the 
fourth, at least in the single specimen which I have of this sex. In the female the third 
joint is equal to the fourth. 
^ The vaginal plates of the female of the European consimilis are apparently wide, 
of nearly equal length and width and arcuate-truncate at apex. 
^ The males have the last ventral segment truncate and a more or less deep de- 
pression at middle of apex. The females have the last ventral segment more or less 
triangular and generally narrowly rounded at apex, without median depression. 
