A Sl/nri:!' SEASON in the nicobar islands. 
97T 
various deposits that make up the whole facies have, with the exception of a 
double outcrop in two parallel lines of true rook, been laid down at some jjeriod 
or other, probably in Eocene times, beneath the surface of the ocean. Camorta 
and Nankauri Islands are for the most part composed of clays that are in places 
so hard that they have all the appearance of rock. Tipper* has shown that 
these clays are generally found near igneous rocks and seem to bo a product of 
their decomposition. The rock-like appearance of these masses of hard clay 
is specially well seen in certain parts of the coast line, where the cliffs have fallen 
away and the resultmg debris now lies as large boulders on the fore-shore, or 
where denser bands of this deposit still resist the gradual wearing away by winds 
and tides and now run in ledges and shelves, exactly like those of a rock reef ^ 
out from the shore. This latter condition is particularly well seen at Naval 
Point on the eastern entrance to Nankauri Harbour, where a small headland 
juts out into the sea. The fauna of the clay masses is an interesting one. From 
the similarity of their appearanee to true rocks one would expect to find them en- 
crusted with Rock-oysters and Barnacles and serving as a habitat for such mol- 
luscs as limpets and Chiton. But as a matter of fact all these are conspicuous by 
their absence and instead we find that the boulders are bored through and through 
with the tube-like dwellings of Pholas and associated with the mollusc in these 
burrows one not infrequently comes across Turbellarian worms, while numerous 
browii-colomed actinians occupy pock-like pittings on the surface. Underneath 
these rocks and boulders I found a large assortment of animal life. Flat little 
PorceUanid crabs, that rapidly dropped off the boulder and scuttled away to 
another shelter, were of frequent occurrence, and numerous other crabs, such as 
Leptodius sp., were found half bmied in the underlying mud. In certain areas 
one could usually manage to find an example of a Gephyrean, apparently be- 
longing to the genus Tludassema, with chocolate-brown body and long yellow 
proboscis. Polychaet worms and Turbellarians were also by no means uncom- 
mon, while small Amphipods were ubiquitous. ' Not infrequently the lower 
surfaces of these clay masses were encrusted with sponges of brilliant hues, red 
yellow and blue being the prevailing tints. 
Dr. von Hochstetter f, of the Austrian frigate “ Novara ” which visited the 
Nicobars in 1858, was the first to pomt out that there is a very distinct correlation 
between the geological formation and the type of vegetation of these islands. 
I have already referred to the difference between the well-wooded slopes of 
Kachal and the open grass-lands of Camorta,and the cause of this difference is 
to be found in the fact that Kachal is composed of limestone and corresponds, as 
regards its geological features, to the southern islands of Great and Little Nicobar, 
whereas with the exception of two bands of upper cretacious rocks, one forming 
the north-east coast of Nankauri Island and the other extending in a dis- 
continuous ridge along the west coast of Nankauri and Camorta Islands, — 'being 
interrupted at the entrances of Nankauri and Expedition Harbours — almost the 
whole of Nankauri, Camorta and Trinkat Islands are composed of a sterile 
magnesian clay.J 
During the process of upheaval from its original submarme level to its present 
altitude the clay strata have in many places been folded and contorted. Along 
the northern shores of the eastern entrance to Nankauri Harbour the exposed 
* Tipper, G.H., “The geological formation of the Andamans with references to 
the Nicobars.” Records of the Geological Survey of India, Vol. XXXV, Pt. 4, 
p. 13, Calcutta, 1911. 
t Hochstetter, Dr. von., “ Contributions to the Geology and Physical Geography 
of the Nicobar Islands.” Selections from Records of the Government of India, 
Home Dept., No. LXXVTI. — ^Pa^jers relating to the Nicobar Islands, Calcutta, 1870. 
J Vide Tipper, “ The geological formation of the Andamans with references 
to the Nicobars.” Rec. Geol. Survey, India. Vol. XXXV, Pt. 4, Calcutta, 1911. 
