SEA-BOTTOMS AND CALCRETES. 151 



are usually fouud in a friable sandy condition,* and thus provide material already 

 disintegrated which can easily be transported by rivers to the sea. The sand forming 

 the floor of the Gulf has, in many places, been cemented in situ into calcareous 

 sandstones or "calcretes," locally known as "paars." In the north part the paars 

 arrange themselves roughly into three groups, running parallel with Adam's Bridge, 

 north-north-west to south-south-east. The first line is found at a depth of 

 3^- to 4|- fathoms, the second at 6 to 8 fathoms, and the third at 9 to 10 fathoms. 

 Further south, on the West Coast, they have a north and south alignment, here again 

 following the outline of the coast. 



It would appear that the calcretes have grown out radially from centres, the 

 smaller ones are mainly circular in outline, while the larger ones seem to have been 

 formed by the growth and fusion of a number of smaller ones. Outliers exist in many 

 cases near the larger paars, which seem to suggest that they too will eventually 

 become fused with the main paars. Dredging and diving operations were mainly 

 conducted in the neighbourhood of the paars, and most of the samples handed to me 

 for examination were obtained from these localities. Hence the descriptions which 

 follow readily group themselves round the most important paars. 



Periya Paar. This is the most westerly of the paars, and lies about 20 miles south- 

 west of Manaar Island. It extends 1 1 miles north-west south-east, and averages 

 about 1^ miles in width. Smaller paars exist as outliers at the northern and southern 

 extremities. The rocky bottom has a depth varying from 8\ to 10 fathoms, with a 

 thin layer of sand covering the flat surface of the calcrete. 



Outside the paar, to the west, the bottom rapidly sinks to 20 fathoms, and further 

 out 80 fathoms and over are reached. Five specimens of the bottom were dredged in 

 the neighbourhood of the paar and calcretes from three localities were broken off by 

 hammers and brought to the surface by divers. 



West and South-west of the North end of Periya Paar, at a 

 depth of 10 fathoms, the contents of the dredge showed many shells in a fresh 

 condition, Polyzoa, such as Cellaria and Scrupocellaria, Halimeda, and numerous 

 Nullipores. These were accompanied by a fairly coarse angular quartz sand. The 

 fine material yielded 27 '64 per cent, of carbonate of lime, and under the microscope 

 was seen to consist of quartz, sometimes stained with iron, many black grains of 

 ilmenite and magnetite, tourmaline and zircon, and, as organic constituents, numerous 

 Foraminifera, Crisia, and sponge spicules. 



North-west of the Paar, at 12 fathoms, Foraminiferal sand with shells was 

 dredged. The shells included Pcctunculus, Area, Chavia, Venus, pearl oyster, and 

 with these, forming the coarse material, were Heteropsammia, Echinoderms and 

 a brown Alga. The smaller forms were Foraminifera Heterostegina in great pro- 

 fusion Nullipores, Polyzoa and Serpula;. Only a few clear quartz grains were 

 present. 



* A. K. Coumakaswamy, ' Geol. Mag.,' August, 1903, p. 348. 



