42 
INSECTA SAUNDEKSIANA. 
darker than any other part of the body, and composed of a fine thick velvet¬ 
like tomentosity. The upper part of the sides is clothed with more or less 
fuscescent tomentosity, coloured like that of the sides of the elytra. 
Finally, the depressed part of the disc is clothed, like the depressed part of 
the elytra, with a more or less whitish, yellowish, fulvescent, ferruginous or 
greenish tomentosity, adorned with fuscescent spots or lined®, the most 
important of which are two apical and two basal ones. The elytra are, in 
all the species, more or less regularly or densely punctate-substriate, with 
their interstices flat ( Pt . depressus only having the appearance of alternate 
interstices subelevated behind), more or less transversely rugulose ante¬ 
riorly. I have found it impossible to use these characters for the distinc¬ 
tion of the species, since not only they have nearly the same degree of 
weight in all the species, but also, with a few exceptions, they vary as 
much between specimens of the same species as between the species them¬ 
selves : their common lighter band varies, as has been said of the thorax, 
not only according to the species, but often in the different specimens, from 
being more or less rubbed or fresh. This band is generally distinctly cir¬ 
cumscribed at its sides, deeply emarginate at the middle and above the 
apex: these emarginations have been produced by the darker ground¬ 
colour of the sides extending inwards, and they are always darker than the 
sides themselves, for these are always more or less mixed with the same 
colour as the band, whilst the emarginations are nearly unicolor, forming 
large more or less triangular maculae (the median), or more or less rounded 
and irregular spots (ante-apical): each of them is rarely transformed (as in 
Pt. virgatus) into two connected oblong lineolae; in this case the band is 
hardly distinguished from the lateral colour (Pt. virgatus and mixtus ): 
finally, in one species, the colour is subequally distributed over the whole 
of the elytra, the sides being scarcely darker than the disc, and this has the 
ordinary dark maculae circumscribed all round by the general colour 
(Pt. viridanus ). From these variations I might point out several differences 
for the distinction of the species, but the most important characters I have 
found are the proportions of length and posterior attenuation of the elytra, 
their depression on the disc, their lateral convexity and inflection, their 
longitudinal outline or profile, their posterior declivity, and, finally, the 
presence or absence of the ante-apical callosities or tubercles, their form, 
&c. The body beneath increases or decreases in thickness according to 
the upper convexity or flatness of the thorax and elytra: its coloration 
uniformly agrees with that of the thorax beneath. The pectus and abdo- 
