646 REPORT— 1902. 



A few heavy minerals occur, but the bulk is made up of clay with minute grains of 

 quartz. Only a few organisms, one Foraminifera, and a small shell fragment were 

 found in a sample examined. 



In the Gulf of Manaar banks are found which shallow towards the middle of 

 the bay and deepen towards the north and west. 



The middle area of the.se banks consists mainly of sand yielding carbonate of 

 limefrom3'09 to 7"04 per cent. On the margins, where shell fragments and Foramini- 

 fera become more abundant, the percentage increases to 22-20 and 34:'32; while on 

 the extreme west, where depths of 80 fathoms are found, the amount becoms 76'50 

 and 85-86 per cent. Some range up to 92-05 and even 95 per cent, of carbonate 

 of lime. 



The sands of the central area include as a rule a high percentage of heavy 

 minerals, but very little is found iu the more calcareous samples. In the Foramini- 

 fera sands Heterostegina is exceedingly abundant. It is accompanied by simple 

 corals such as Heteropsammia, I'olyzoa, Pteropods, the spat of young Oj'sters, Echino- 

 cyamus, Xullipores, a red branchina- Foraminifera like Polytrema, and Diatoms. 



On the west coast, south of Chiiaw, at 85 fathoms, the dredge brought up 

 enormous quantities of Nullipores of a white or greyish colour. These were mostly 

 globular in form and ranged up to 2 inches in diameter. On breaking, the interior 

 was in many cases red in colour. Sections of these showed fresh gi'owth of the 

 plant on the oviter margin and broken-down tissue in the interior. Imbedded in 

 the plant structure were numerous sand grains consisting of quartz, garnet, tour- 

 maline, and magnetite. While these inclusions mostly occur in lines they show 

 no selection of grains into sizes. They have probably been inclosed by irregular 

 growth on the part of the Nullipore, and some may have filled the crypts formed 

 by Lithodomus borings. The breaking up of the tissues and oxidation of the fer- 

 ruginous grains account for the red staining of the interior. 



One or two points may be mentioned regarding the deposits as a whole : 



1. Some, such as in Galle Bay and Palk Bay, are evidently very old. They re- 

 present the remains of a fauna where solution and chemical changes have been at 

 work. The shells left are mostly composed of calcite, not aragonite, and chemical 

 analysis shows that many of the shells have become partially converted into phos- 

 phate of lime. 



2. In all the cases where Sponges like Gliona have bored into shells they are 

 calcite, not aragonite. It would not be safe to assert thatCliona never bores into 

 aragonite, but it certainly holds good in those specimens I have examined both 

 from the Indian Ocean and other places. 



3. The inorganic minerals which are found in all the deposits such as quartz, 

 garnet, kyanite. &c., are stable, and resist dissolving agents. The fact that other 

 less resistant minerals are found in casts of shells leads to the conclusion that these 

 may have been removed since the sands were laid down. 



4. In drifted deposits a relation exists between the size or weight of the inor- 

 ganic and organic constituents. Where large shell fragments are found large 

 minerals also occur. This fact might be useful in determining cases where other 

 evidence of drifting is not conclusive. 



My thanks are due to Professor Herdman, who has helped me in the determina- 

 tion of some forms, and to Mr. C. C. Moore, F.I.C., for the care he has taken in 

 analysing the deposits. 



C. Notice of a hitherto unrecorded Element in the Occipital Bone of Seals. 

 By Professor Cleland, F.R.S. 



I have long been aware of the bony element which I now show in the skull 

 of a young hooded seal, Stemviatopus cristatus. It corresponds exactly with the 

 paroccipital of Owen in osseous fiehes. It articulates behind with the broadest 

 part of the supraoccipital, in front with the mastoid, above with the parietal, 

 and below with the lateral element of the occipital bone called exoccipital by 

 Owen. I have not hitherto 'called attention to it because I waited till I could 

 find out if it ocpurred io seals generally, Sir William Turner has given me the 



