130 
Psyche 
[December 
be seen in Plate 10, Fig. 2, it forms the rigid framework 
which permits an effective pumping action. With patience 
and care the floor of the pump can be loosened at the edges 
and gently lifted off. This exposes the ventral aspect of the 
roof of the pump, not otherwise visible. The structures 
exposed are shown in Plate 11, Fig. 5. Here one can see 
the relationships of the hard parts to the membrane and 
open up the transverse fold to expose the first and second 
toothed ridges, as shown in Plate 11, Fig. 3. Plate 11, Fig. 
4, shows a lateral view with the side of the floor of the 
pump cut away. Here the setae-like teeth are seen in de- 
tail. They are strikingly like those found in Notonecta, 
which are shown in Plate 11, Fig. 2. Note that, in Pelo- 
coris, the teeth associated with this bar are not directly 
connected to it as in Notonecta , but are instead attached 
to it by means of a membrane. The sclerotized bar does not 
articulate with the floor at the lateral margins, but instead 
ends in a membranous connection. There is no dorsal bar 
in the cibarial region as there is in Notonecta. 
The purpose of this pharyngeal armature is not fully 
understood. It is not clear from the action of the parts 
exactly what role they play in the ingestion of the food. It 
may be supposed that the teeth serve some sort of straining 
function and perhaps act to break up clots in the food ma- 
terial. When the apodemie is worked back and forth the 
second set of teeth appears to rub over the third set much 
as one might clean a comb with a brush. Such action might 
be supposed to prevent the clogging of the teeth with food 
material during feeding. The action of the first set of 
teeth, which extends only part way down the sides, has 
not been determined. Plate 10, Fig. 1, shows a composite 
stereogram of the entire structure with the lateral wall of 
the pump cut away. It will help the reader to orient the 
various structures in relationship one with another and 
with the head as a whole. 
Discussion 
A detailed comparison of the pumps of Notonecta, Pel- 
ocoris, and Hesperocorixa is necessary before any assump- 
tions can be made concerning the relationships between 
