[II.] 



ROCK SPECIMENS. 



BY T. COOKSEY, Ph.D., B. Sc., 

 Mineralogist and Chemist, Australian Museum. 



THE following are brief Notes on the Rock Specimens collected 

 by Mr. C. Hedley : 



Coarse Sand. A specimen of coarse sand from the western 

 sea beach of the Atoll, consists principally of waterworn frag- 

 ments of coral and coral rock, comminuted or small shells, the 

 tests of the Foraminifera Orbitolites complanata, Tinoporus bacn- 

 latus, and to a smaller extent Polytrema muriaceum, Amphistegina 

 lessonii, and a few fragments of Echinoderms. It is entirely 

 calcareous. 



Calcareous Conglomerate. A calcareous conglomerate was 

 obtained from the bore put down at Luamanif, on the southern 

 sea coast of the islet of Funafuti, at a depth of ten feet. The 

 mass is rather loosely cemented together, and the individual 

 particles are similar to those composing the beach sand. Their 

 relative quantities, however, differ somewhat. The tests of 

 Orbitolites complanata although numerous, do not form such a 

 large proportion of the mass, while those of Amphistegina lesscnii 

 are much more numerously represented. It also contains well 

 worn pebbles of coral rock up to one inch and one inch and a half 

 in length. A thin layer of carbonate of lime encrusts all the 

 components and forms the cementing material. This coating has 

 previously been noticed by Mr. J. E. Carne* to occur on surface 

 sand at Norfolk Island. 



Conglomerate. A firmly coherent conglomerate containing 

 similar materials to those of the preceding rock, the tests of 

 Orbitolites complanata, however, appearing to be relatively still 

 less numerous. The mass consists more especially of waterworn 

 pieces of coral-rock, with a large proportion of the tests of both 

 Tinoporus baculatus and Amphistegina lessonii. It is much con- 

 solidated by a deposit of carbonate of lime around each separate 



* An. Rep. Dep. Mines, N.S.W., for 1885, p. 145. 



