386 FRANCIS DARWIN. 
shaped saw, and must, therefore, have three cutting 
edges. 
Along the concave border, in Fig. 1 (the ventral aspect) 
may be seen four pairs of teeth (vt, vt, &c.), making in all 
eight projecting points; these unite in forming one of the 
cutting edges of the saw. We obtain a bird’s-eye view of this 
same edge in Fig. 2, where the symmetrical teeth (vf, vt) may 
Fic. 2.—Bird’s-eye view of the ventral aspect of the proboscis. 
ot vt. Ventral teeth meeting in pairs on either side of the 
median line (). 
g. Narrow groove occupying the angle of the roof-like ridge of 
which the ventral aspect consists. The roof is supposed to 
rise towards the observer, g being merely a crack running 
along the roof-tree. 
b. Barbs. 
o. The orifice or external opening of the channel or tube of the 
proboscis. 
p. See text. 
“bh 
be seen meeting each other in pairs along the line (g). The 
two other cutting edges of the bayonet-saw are formed by 
teeth projecting from the dorsal margins of the two lateral 
surfaces. One of these cutting edges is seen in profile in 
Fig. 1 (dt, dt). lf we imagine a saw with a broad back, 
having a cutting edge along each margin of the Jack, as well 
