574 DR. J. W. EVANS ON MECHANICALLY-FORMED [Aug. I9OO, 



VII. Other Tropical and Subtropical Deposits of like Nature. 



Calcareous rocks, having many characters in common with those 

 which we have been considering, are found in many other localities 

 in warm countries. I am not aware, however, of any in which 

 foraminifera play so important a part. This may be due to the fact 

 that very few of these deposits have yet been submitted to close 

 microscopical examination, and that each grain is usually surrounded 

 by an envelope of deposited carbonate of lime which hides from view 

 the nature of the nucleus. 



These beds.may be roughly classified as follows : — 



(a) Those formed under the surface of the sea, and con- 

 taining unbroken remains of marine organisms 

 larger than the grains of which the rock is 

 composed. 



Deposits consisting of aggregations of calcareous particles derived 

 from the action of the sea on coral-reefs occur in the neighbourhood 

 of almost all coral-islands. It is stated by Dr. Guppy \_26~] that in 

 the Cocos-Keeling Archipelago such deposits form to the leeward on 

 the flanks of every coral-reef. He intercepted some of the material 

 as it was carried along by the current : it consisted mainly of 

 amorphous calcareous grains, with a small proportion of alcyonarian 

 and sponge-spicules. It would have been interesting to ascertain 

 by the examination of thin sections whether any of these amorphous 

 grains consisted of a calcareous particle as nucleus, surrounded 

 by deposited carbonate of lime, as in the case of the grains of the 

 Junagarh Limestone. There can be little doubt that the banks formed 

 in this way are false-bedded. See also [15] p. 339 & [46] p. 18. 



The Nga-tha-mu beds of the island of Kau-ran-gyi (Ko-ran-ji) 

 on the Arakan coast of Burma and the mainland opposite, which are 

 said to resemble the Porbandar Stone, but contain echinoderms, 

 molluscs, and other fossils [21], fall under this heading. They are 

 included in the Pegu Beds, which are supposed to be of Upper 

 Tertiary age. 



(b) Littoral deposits composed of calcareous material 

 thrown up by the waves. 



These deposits resemble in many respects the strata of sub- 

 aqueous origin included in the previous class. The grains have 

 usually an envelope of deposited carbonate of lime, and oolite-grains 

 are not uncommon. The larger fossils are, as a rule, in a fragmentary 

 condition. Pebbles of limestone as well as of other rocks sometimes 



t idal limits, and there is every reason to suppose that the presence (if Camjjtonyx 

 on Girnar dates back from a period when only the upper part of the mountain 

 rose above the sea. I am indebted to Dr. Blanford for the identification of this 

 mollusc, individuals of which were adherent to some of my rock-specimens. 



