On a remarkable new Ball-rolling Beetle. 433 
cell almost pointed on the radius, the second transverse 
eubital nervure curved. Apex of the radial cell a little 
further from the apex of the wing than from the apex of 
the stigma. 
Hab. Houei Sai, Haut Mékong, June 6-10, 1918. 1 ¢. 
Possibly a form of Agathis maculipennis, Brullé, which it 
resembles in colour, but the second fuscous spot on the fore 
wing is absent in the present species. Brullé’s description 
is not sufficient to indicate whether his species should be 
placed in Huagathis or Disophrys. 
XLIUL—A remarkable new Buall-rolling Beetle 
(family Scarabeeide). By GitBert J. Arrow. 
(Published by permission of the Trustees of the British Museum.) 
A SINGLE specimen of the extraordinary insect here repre- 
sented, bearing no label to record its origin or habitat, was in 
the collection of the late B. G. Nevinson, recently. presented 
to the Britis Museum by his son. Probably, like its nearest 
allies, it inhabits the western part of Southern Africa, possibly 
the Bihé district of Angola, from which Mr. Nevinson 
received other interesting beetles. The specimen is a male, 
aud the great enlargement of the fore legs is no doubt 
distinctive of that sex. The enormously thickened front 
femora seem to indicate great muscular power, and the 
strangely shrunken intermediate legs appear more singular 
by contrast. ‘lhe insect is a striking example of speciali- 
zation by successive atrophy of its members. The front tarsi 
have disappeared in all the ball-rolling Scarabeidew ; the 
wings also have gone in the present genus, and here we seem 
to be advancing towards a reduction in the number of legs 
from six to four. 
I refrain from establishing a new genus for this species in 
view of the unsatisfactory character of several of those at 
present recognized in the group. I can find no sufficient 
reason for separating Pachysoma and Mnematium. Although 
M. silenus, Gray, has the middle coxz apart, the type-species, 
M. ritchit, has not, and the features relied upon by Macleay 
for its severance from Pachysoma have been found to have 
no importance. Similarly, there seems no adequate ground 
for separating AZnem itidium trom S-vbasteos, 
Mnematium cancer, sp. n. 
Nigrum, nitidum, glabrum, corpus depressum, latissimum, capite 
antice 6-dentato, supra haud dense tuberculato, pronoto hic et; 
illic minute punctato, lateribus serratis, basi leviter sinuato, 
