IOWA ACADEMY OF SCIENCES. 
73 
the dentes are borne rows of long, strong hairs or bristles 
which present an almost solid surface to strike the water. 
The mucrones are of very unusual form, being flat and 
spoon-shaped and with their ends turned in toward each 
other. In another unrelated genus we find a modification 
for the same purpose which differs somewhat. Fig. 12. 
In this species, Podura aquatica Limie, the manubrium 
is extremely short and each dentes has an outward direc- 
tion from its base to near its middle where there is a bend 
that appears almost a joint. Beyond this bend, the dentes 
turn inward again. The mucrones are flattened some- 
what as in the Sminthurus just mentioned. 
