50 
Genus Chalastinus, nov. gen. 
Head narrow ; antenniferous tubercles prominent. Antennae 
slender, elongated, 11-jointed in both sexes, the terminal joint 
shorter than the preceding, filiform ; the third and five follow- 
ing joints thickened at the tips and curved, especially in the S • 
Thorax much narrowed anteriorly, scarcely perceptibly tubercu- 
lated on the sides. Elytra subtrigonal, depressed, rounded to- 
gether at the tips. Mesosternum bituberculated, hind margin 
sinking behind into a fovea in common with the fore edge of the 
metasternum. The fore tarsi of the <S not dilated, but fringed 
with fine hairs. 
This genus has a great resemblance in general figure to Thry- 
allis (Thomson, Class. p.31); but the antennse in Thryallis have 
only ten joints, and the sterna are broad and plane, the pro- 
sternum especially being remarkably broad. The Anisocerinse 
vary to such a degree in these and other parts of structure, that 
almost every species might be made into a separate genus, if we 
attached the same importance to those characters in this as in 
other groups of Coleoptera. 
Ch. Egaensis, White. 
Anisocerus Egaensis, White, Cat. Long. Col. in Brit. Mus. ii. p. 408. 
The typical form of this species seems to be confined to the 
neighbourhood of Ega, on the Upper Amazons. It has on each 
elytron behind the middle a short, oblique, ochreous belt, com- 
mencing on the sides near the middle, and not reaching the 
suture, near which, in a line with the belt, is a round ochreous 
spot. This is common at Ega on decaying branches of trees in 
the forest. The following slight local modification was found 
only at Fonte Boa, 120 miles in a straight line north-west of 
Ega. 
Local var. Ch, postilenatus. Like the type, except that the 
oblique ochreous belt of the elytra is continuous from the sides 
to the suture, and is also prolonged as a stripe along the sides 
to the shoulders. 
This variety wholly replaces the Ega form at Fonte Boa. At 
Cayenne a nearly allied undescribed form* occurs, which, al- 
though apparently very difierent from Ch. Egaensis, I believe to 
be a local modification of it. A species which varies in a small 
degree from locality to locality a short distance apart becomes 
modified in a greater degree in a more remote district and under 
more greatly changed local conditions ; at least, the distribution 
* This is extremely rare in collections ; and I regret being unable, from 
having no specimen at command, to give a description of it. 
