45 
always impinges upon the eyes, a submentum with the anterior 
margin arcuate, fig. 7, a scutellum of the usual form, anterior 
tibia with only a single tooth at the middle, fig. 1, or even 
without, fig. 10, and middle and posterior in general without 
the lateral tooth. The beetles included here are the dominant 
forms. They are very dark, almost black, and in general quite 
opaque throughout, only a few showing on the head and pro- 
thorax the smoothness and mahogany color which is so charac- 
teristic of the females and of the members of the first group. 
These I would consider as having become most specialized 
along lines of degeneration. Among the members in this as- 
sembly will be seen the greatest amount of minor variations 
and signs of unstableness. The specimens as a whole show 
a great degree of reduction and simplification of structure as 
well as peculiar modifications and they vary also greatly in 
size, many of the less developed being much distorted and 
asymmetrical. The mandibles may be large or small, have 
a large tooth, fig. 4, or one much reduced but never absent, 
though the usual is with one of moderate size, fig. 1. In a 
few specimens the tooth is short and very broad at base, 
and in a number there is an additional but very small denticle 
not far from the apex of the mandible. The clypeus though 
generally straight along its anterior margin, may in some of 
the larger individuals show a bi-emarginate margin though 
never to such a marked degree as seen in group one, or a 
tendency toward the triangular shape so characteristic of the 
following group. In one or two of the more extreme phases, 
the margin is retracted and emarginate and in several almost 
evenly arcuate. The submentum is trapezoidal in a few of the 
larger specimens, though in the majority, simply arcuate, fig. 7. 
The sides of the head are, as a rule, as shown in fig. 1, though 
there is a great degree of variability as to the details of the 
outline, especially as to the prominence of the canthus and its 
relationship to the eye. The scutellum is generally normal, 
fig. 1, but in a few, great instability is shown by its assuming 
unusual shapes, as when the lobe becomes greatly elongated 
or quite triangular. The fore tibiae are, as indicated, in general 
quite simple as to the shaft but often variable as regards the 
apex. In the middle and hind tibiae, the shaft is usually 
