86 
is due to imperfect development or to some attrition to 
which the parts in question have been exposed by the habits 
of the insects I cannot say, but it is certain that specimens 
are frequent in which sharp teeth on the tibiæ are repre- 
sented by mere blunt sinuosities, and sharp carinæ on the 
pronotum and conical tubercles on the elytra are represented 
by eorresponding blunt elevations having all the appearance 
of having been rubbed down. Perhaps it may be thought 
that I may be in error in regarding these variations as non- 
specific, but I can say positively that they are so, as I have 
found them in varying degrees in specimens differing in no 
other way and taken in company. All the above characters 
have been treated as specific in most of the published de- 
scriptions of these insects, doubtless through the descriptions 
having been founded on the inspection of only one or two 
specimens, and doubtless they are specific if regarded merely 
as indicating the normal characters, but they are clearly not 
available for reliable identification of the species. 
The following characters I have found invariable, and as 
I have examined large numbers of specimens of some species 
they must at any rate be only very rarely variable: — The 
setulose vestiture, the texture of the inequalities of the sur- 
face (whether glabrous and nitid, or more or less setiferous, 
or more or less punctulate, or of an apparently spongiose 
tissue), the relation of the subsutural carina of each elytron 
to a short basal carina which borders the external margin 
of the scutellum: in some species the latter is straight and 
altogether disconnected from the former, in others the for- 
mer is bent outward at the apex of the scutellum and runs 
forward in a curve to meet the latter (it must be noted that 
the subsutural carina, so-called, is not always a continuous 
carina, but may be broken into short pieces not quite touch. 
ing each other), the general disposition of the elytral 
tubercles. Regarding this last-named character it is to be 
observed that it is quite distinct from the question of the 
size and shape of individual tubercles, or the extent to which 
this and that tubercle are run together into a short carina 
(which, as noted above, are very variable). To make this 
clear it is necessary to adopt a name for the tubercular series 
of the elytra. If an elytron of almost any Australian Troz 
be examined there will be seen ten longitudinal ridges of 
some kind; in almost all the species they are more or less 
tuberculiferous, and may or may not be the intervals be- 
tween defined striæ; the first of them is close to the suture 
(I have called it the subsutural carina), the third is almost 
always, and the fifth is frequently, a narrow, continuous 
carina in its basal part. These ten ridges I have called the 
"systematie series," in Latin “series normales.” In many 
