Fossil Mammalia associated with Stone Implements. 445 
rock; they seem rather to be related to faulting and shearing of the 
limestone at its junction with the schists. Surface specimens of the 
limestone are usually somewhat coarsely crystalline, and white or grey 
in colour, with few impurities save quartz. Lower down in the 
workings they are often black or reddish in colour, and closely resemble 
the Carboniferous Limestone of Somersetshire. Under the microscope, 
however, they differ 2 ¢oto, having a foliated structure in even the 
most compact-looking specimens. It is probable, therefore, that the 
sugary appearance of the outcropping rock is due to some form of 
surface alteration. It cannot be attributed to pressure or contact 
metamorphism, as it would in that case be just as apparent below 
ground as it is above. The limestone is highly magnesian and some- 
times approaches a true dolomite in composition. No definite silicate 
minerals can be detected under the microscope. 
The feature of the ore-body with which we are now chiefly 
concerned is the extraordinary accumulation of mammalian bones in 
No. 1 Kopje. Beautifully crystallised phosphatic minerals have also 
been found in No. 2 Kopje, but although it would seem a natural 
inference that they are due to the interaction of the metalliferous 
solutions with the lime phosphate of bones, none of the latter have 
been met with. The amount of bones in No. 1 Kopje is enormous. 
They occur in the central part of the kopje and almost continuously 
beneath it, below the level of the surrounding flats. It would appear 
that the bone deposits represent the infilling of a large cavern in the 
limestone, perhaps with a kind of swallow-hole leading down from 
the top of the kopje, though there is no actual opening at the present 
time. It is difficult from the data at present available to determine 
with any certainty the relative ages of the different layers of bones, 
but their accumulation must have taken a very long period of time. 
There are masses of bones almost free from other substances, and 
there are interspersed muddy layers containing zine compounds, but 
free from bones. Much of the material, however, which shows no 
large bones, yields on disintegration innumerable bones of rats, shrews, 
birds, etc. The bones are in nearly all cases partly or wholly 
converted into zinc phosphate (hopeite?). They are therefore truly 
fossil, the organic matter having disappeared, and having been 
completely replaced by mineral substances. Vughs in the deposit 
are often lined with magnificent crystals of the rare mineral hopeite, 
and they also show at times more or less dendritic coatings of 
a substance which at first was taken for amorphous zine phosphate, 
but which is rich in vanadium, and may really be a calcium vanadate. 
The new triclinic zinc phosphate ‘tarbuttite’ occurs in No. 2 Kopje, 
with cerussite, hemimorphite, hopeite, pyromorphite, and vanadinite 
or descloizite, and does not seem to be found in the bone deposit. 
The bones make up vast accumulations of isolated broken frag- 
ments. Whole bones are the rarest exceptions, and are exceedingly 
difficult to extract even when discovered. There never appear 
to be a number of bones belonging to the same animal occurring 
together, as would be the case if they had died naturally on the 
spot, or been accidentally engulfed, in the way suggested for the 
well-known occurrence at the Winnats, Castleton, Derbyshire. It 
