378 GEORGE H. CARPENTER AND MABEL C. MACDOWELL. 
the analogous structures in another onisciform larva, that of 
the staphylinid Syntomium geneum (Schiodte [’73],pLxx, 
fig. 5). The convex lobes in the latter bear sharper and 
strouger spines, while the teeth of the semicircular row are 
more numerous. Also, beneath the labrum of the Syntomium 
larva two little rows of teeth occur far to the front of the 
semicircular row. 
The tentorium (PI. 35, fig. 10, ten.) is thin and transparent, 
with each antero-lateral lobe deeply cleft. In this larva the 
sclerite of the head-capsule is not continuous beneath the 
labium, the two cheeks being connected only by the tentorial 
plate. 
Mandibles. (PI. 35, figs. 1-6.) 
As noted by Polph ( ? 74, p. 28), the shape of the mandible 
varies according to the age of the larva. Three stages in 
the development of this organ are drawn in figs. 1-3, the 
sequence of the figures indicating the comparative size of the 
specimens. In its simplest stage (fig. I) the apex is quite 
blunt and almost rounded, but as growth proceeds it becomes 
sharp and pointed (fig. 2), and eventually, in the full-grown 
larva, bifurcated (fig. 3). 
As to the actual form of the mandible, very little can be 
added to Rolplds accurate description. The inner surface 
bears no lateral teeth, but is furnished with fine tufted hairs 
arranged in two bunches (fig. 1, 7i.). Pig. 5 shows the 
branched apex of one of these hairs. Beneath them there is 
a very curious comb-like process (pr.) jointed to the mandible, 
and bearing along its free edge from eight to ten teeth 
arranged in a semicircle. The two lateral ridges of this 
process are strongly chitinised, the anterior ridge showing a 
transverse cleft and being prolonged iuto a sharp apical tooth 
(fig. 4). The molar surface of the mandible is a strong 
grinding structure, grooved and ridged like a file, the ridges 
numbering about thirteen (fig. 6). Both at the top and base 
occurs a tuft of sensory hairs, similar to those found more 
