586 Wisconsin Academy of ScienceSj Arts , and Letters. 
hairy, membranous inner one, the suture being indicated by a 
conspicuous row of hairs. 
C. The earth-boring dung-beetles show a deviation in the 
following organs: 
a. The epipharynx is chitinized and attached to the labrum 
along its entire anterior and lateral margins; the arrangement 
of its hairs and sense-papillae is less definite and regular. 
b. The mandibles become more chitinized and end in one or 
more sharp teeth; the proximal one is formed by the lacinm’, 
which is partly chitinized and partly membranous. The con- 
junctivus, which is still conspicuous in Geotrupes, becomes 
more and more obscured, and has almost entirely disappeared 
in Bradycinctus ferrugineus (compare Figs. 39, 49). The 
molars are reduced in size. 
c. The maxillae show a change in both galea and lacinia; 
the mass of fine hairs disappears and is replaced by a few 
stouter ones, the parts becoming slightly more chitinized and 
toothed. 
d. The mentum becomes chitinized at its front edge, and a 
fusion of the lobes along the median line is here first notice¬ 
able. With this fusion goes a reduction of the hypopharynx. 
D. The skin-beetles. In this group the entire set of trophi 
has become more strongly chitinized and armed with stiff 
hairs adapted for brushing and scraping. The group is rep¬ 
resented by one genus, Trox (Figs. 48-51). 
a. The epipharynx is no longer a separate fold; it shows a 
distinct reduction in size; the front and lateral edges of the 
labrum are turned in, enclosing a space which is covered by a 
membrane, the epipharynx. 
b. The mandibles have become so thoroughly chitinized as 
to obscure their segmentation; the maxillae show a greater de¬ 
velopment of the teeth on galea and lacinia. 
c. The labium shows a decided reduction in hypopharyn- 
geal structures, and the labial lobes have fused along the medi¬ 
an line to form one broad plate. 
2. The Leaf-chafers. These are all herbivorous, and we 
should naturally not expect to find a great difference in mouth- 
parts between members of the group. Comstock (2) divides 
