154 JOURNAL OF SCIENCE. 
not formed in their present position, it does not necessarily follow 
that they have come from a very great depth. 
On the other hand, the occurrence of carbonaceous shale in 
the walls of the mine, and the fragments of the same rock found 
in the diamond breccia itself, offer a ready explanation of the 
origin of the carbon from which the diamonds were formed ; and 
the undoubted fact that Kimberley mine, which is surrounded by 
shale, is much richer than any of the others, gives additional 
weight to this hypothesis. It has indeed been supposed that 
hydro-carbons derived from the shales, when under great »res- 
sure and at a red heat, may have been decomposed by metals 
and the carbon set free. And as there would also be present 
compounds containing nitrogen, derived from the decomposed 
vegetable matter, the carbon under these conditions would crys- 
tallise in the form of the diamond. 3 
Thisis a point which future exploration may settle. For if 
the second hypothesis be true, diamonds will cease when the car- 
bonaceous shales have been passed through. 
THE DISTRIBUTION OF TERRESTRIAL 
CRUSTACEA 
<—— 
BY CHAS.” CHILTON, M:A, 
———SS 
The distribution of terrestrial crustacea is a subject which 
appears to have attracted little or no attention from naturalists 
as yet. I can find no mention of it either in Darwin’s “ Origin 
of Species” or in Wallace’s “Island Life.” This is, of course, 
by no means to be wondered at. . There have been, and still are, 
so many problems to be solved in connection with larger and 
more prominent groups of the animal kingdom, that naturalists 
have had plenty to occupy themselves with; and, besides, our 
knowledge of terrestrial crustacea is as yet too limited to allow 
of any very general conclusions being arrived at. Still the sub- 
ject is one of great interest, and will ultimately be of importance 
for testing and confirming the conclusions drawn from the study 
of other groups regarding the origin of the fauna of any country, 
and it is rather in the hope of drawing the attention of others to 
the subject than of doing anything to dispel the ignorance sur- 
rounding it, that I am now writing. 
There are terrestrial species belonging to the Amphipoda as 
well as to the Isopoda, but the former are few, and are found 
only in a few countries, so that my remarks will be applied chiefly 
to the Isopoda. The terrestrial Isopoda are commonly known 
as woodlice, carpenters, &c., and belong to the genera Ovnzscus, 
Porcellio, Armadillo, &c. The great difficulty in accounting for 
their present distribution lies in the absence ofany known means 
of dispersal. In this they resemble the landshells, but their case 
