THE WATER CABINET, 119 
plate are fixed two other convex ones, so broad as to 
cover the whole nose and temples—that these can open at 
pleasure, transversely, like a pair of jaws, so as to expose 
the nose and mouth, and that their inner edges, where 
they meet, are cut into numerous sharp teeth, or spines, 
or armed with one or more long sharp claws—you will 
have as accurate an idea, as my powers of description can 
give, of the strange formation of the under lip in the 
larva of Libellulina, which conceals the mouth and face, 
precisely as I have supposed a similar construction of 
lip would do yours. You will probably admit that your 
own visage would present an appearance not very engaging, 
while concealed by such a mask; but it would strike still 
more awe into the spectators, were they to see you first 
open the two upper jaw plates, which would project from 
the temples like the blinders of a horse; and next, having, 
by means of the joint of your chin, let down the whole 
apparatus and uncovered your face, employ them in seizing 
any food that presented itself, and conveying it to your 
mouth. Yet this procedure is that adopted by the larve 
of the dragon-fiy, provided with this strange organ. While 
it is at rest, it applies close to and covers the face. When the 
insects would make use of it, they unfold it like an arm, 
eatch the prey at which they aim, by means of the man- 
dibuliform plates, and then partly refold it, so as to hold 
the prey to the mouth, in a convenient position for the 
operation of the two pairs of jaws with which they are 
provided. The form of this masked jaw is represented, 
but not very clearly, in Rennies’ “‘ Insect Transformations,” 
p- 164. 
