XXVI 
FASCICULI MALATENSES 
sides are more or less precipitous at all points, in many places so much so 
that there is no lodgement for soil, and vertical crags are exposed. Thus the 
hills, though they are certainly not more than about six hundred feet in 
height, have a massive and solid appearance, belied by the fact that they are 
penetrated in all directions by natural tunnels, which here and there expand 
into lofty domed chambers of considerable extent. Bultit Tapang and Bukit 
Bayu, in fact, are precisely similar in geological formation to many hills and 
islands on both sides of the Malay Peninsula. The stone of which they are 
formed is highly crystalline and has been exposed to metamorphic action of a 
kind that leaves little hope of the discovery in it of organic remains. It is 
evident that they represent the ancient land surface, now much eroded, through 
which the central range of plutonic rock has been erupted. In certain places, 
especially in the neighbourhood of Kampong Jalor and Tanjong Luar, the 
two formations meet and become confused together in a very curious way, and 
in such localities metalliferous veins appear to be common. 
The fauna of Bukit Tapang and Bukit Bayu may be divided into two 
distinct sections, one of which is foundon the exterior, while the other inhabits 
the caves. The former is prolific, for the vegetation that grows in the scanty 
soil which covers the limestone is more luxurious than might be expected from 
the rapidity with which the ground dries up after rain, and rich vegetation 
always means a rich fauna. It is noteworthy, however, that the fauna of these 
hills is by no means so characteristic, to all appearance, as the flora, which 
differs, on the one hand, from that found on granite mountains like Bukit 
Besar, and, on the other, from that which covers marine or semi-marine cliffs 
like those of Chau Mai or the islands of the Taleh Sap. Speaking generally, 
while the number of tall trees, epiphytes, and ferns is smaller than it would be 
in the former situation, the number of fleshy-leaved or fleshy-stemmed species 
is smaller than in the latter. The animals are mostly those found in the plains, 
though certain species, for example, the Malay serow, or 1 kambtng gurun' 
(Nemorbaedus sweitenbamt), do not occur on level ground. This antelope, 
the only one that penetrates down into Malaya, is especially common 
on limestone hills of the kind, taking shelter from the rain in the caves; but it 
also abounds on Bukit Besar. The avi fauna is not particularly noteworthy ; 
an ant thrush (Pitta cyanopterd) becomes common at the base of the cliffs in 
November, and is partly responsible for the heaps of broken snail shells at the 
mouths of the caves, but a species of Mytophonevs, whose cry we frequently 
heard, probably contributes its share, for on a previous visit one of us collected 
a young specimen in just such a place on Bukit Tapang. Insects are rather scarce, 
but in some patchesofjunglethe tailor ant (Oecopby/la smaragdtnd) is so abundant, 
