200 
[vOL. XII. 
Tieconh of the Geuluyical Siii'vej/ of Indut, 
gneiss surface, but it can only be a few feet below the local surface of the slope ; 
it is only reasonable, therefore, to look upon them as ruins of the once existing 
conglomerate bed forming locally the base of the Kadapa rocks, which was nearly 
all removed by denudation. In view of the enormous amount of denudation the 
shapes of the Nagari mountains show them to have undergone, there can be no 
difficulty in accepting this solution of the problem. If the bloeks be not, however, 
really in situ, their existence in their joresent position is even more remarkable, as 
no known agency, but that of floating ice, can explain their presence. The appeal 
to glacial agency in such a southerly latitude would not be justified except on the 
very strongest evidence. 
The character of the rocks in the Pyanur area changes slightly, the included 
boulders and pebbles in the conglomerates are more fre- 
The Pyamu aiea. quently of gneissic origin and less exclusively of quartzite. 
They are embedded in equally soft and uncompacted beds. Fossils are very 
rare; none were found except in a friable sandstone exposed in the left bank of 
the hTagari river opposite Chittapuram, a little below the junction of the Trit- 
tani river. Fragments of TteniojAeris and Dictijozamites were here obtained. 
The basement conglomerate in many parts of the Pyanur area was deposited 
around and includes large water-worn masses of gneiss forming boulder beds 
similar to those occurring in the base of the plant beds at Utatur and elsewhere 
in Trichinopoly district, and similarly at various places in the Ongole groujD of 
outcroj)s in Hellorc disti-ict. 
The hard white and mottled shales so typical of the Sripeimatur gi’oup in its 
proper basin do not occur in any of the outcrops in the Arcot district, but some 
of the clays exposed in the south-eastern corner of the Alikur area show signs of 
passing into a shaly condition, and appear to do so further to the north-east in 
the valley of the Alikur nullah. 
Outcrops south of the JPdldr .—The petrological features of the southern or 
Mamdur group of outcrops, as well as their geographical 
IVHmdar patches. proximity, justify their being assigned to the Sriper- 
matur division of the Rajmahal beds. As they were visited only by the late 
Mr. C. AD. Oldham, it will be better to quote the description, as far as possible, in 
his oum words as given in his notes. 
The three most westerly outcrops, which have already been mentioned as lying 
about twenty miles south-west from the Mamdur group, 
Thcchur outlier. situated close to the village of Thechur, seven miles 
south of Arni. Here to the south-west of the village occurs a “ greenish-yellow 
shaly sandstone,” 'which “ is also dug out from wells in the village. East of 
the village I noticed another minute patch.” 
Of the patches forming the Mamdur group, Mr. Oldham remarks in his notes: 
At Couteantandalam, the most easterly of these localities, 
C'onteautandalam. goveral wells and bowries, in and near the village, expose 
about 12 feet of these beds,” which arc chiefly a soft yellow sandstone thick- 
bedded, but in the lower portion some harder compact bods occur; and a coarse 
conglomerate containing numerous pieces and pebbles of quartz and gneiss in a 
hard silicious matrix has been quarried to some extent from under the soft bods. 
