R. D. Verbeek — Geology of Sumatra. 485 



marls, clays, and very fine-grained sandstones, partly of tufaceous 

 nature. It is most probable that the materials of the greater part of 

 these rocks were derived from volcanic rocks, but on the Island of 

 Nias itself no such rocks occur. 



The beds of marls, clays, etc., are very much dislocated, and vary 

 much in direction and in dip ; they are seldom horizontal. They have 

 a bluish-grey colour ; and are probably of Miocene age, according to 

 Dr. 0. BSttger, to whom I submitted some of the fossil Conchifers 

 and Gasteropods from these marls. 



In the neighbourhood of Goenoeng-Sitolie, the chief place of the 

 island, and also at some other localities, the marls are covered by an 

 unconformable limestone. 



It is remarkable that this limestone, probably (from its discordant 

 position) of late Tertiary age (Pliocene ?), contains, besides indistinct 

 fragments of Corals, some small Nummulince. It is a new proof that 

 this genus not only occurs in rocks of Eocene age, but in younger rocks 

 too. The diameter of the Nummnlinos from the Nias limestone is 

 three millimetres, the thickness 1 to \\ millim. ; they have eight 

 whorls, about 150 chambers, the central chamber is small ; their in- 

 ternal structure resembles very much that of the Eocene, N. Pen- 

 garonensis, Verb., from Borneo, and perhaps they are a small variety 

 of that Nuinruulite. 



The position of the different rocks in the neighbourhood of Goeneng- 

 Sitolie is shown in the Section Fig. 3. 



For those who feel interest in the Geology of Sumatra, I add a 

 list of the principal geological papers on parts of that Island. 



1. F. Valentijn. Oud en Nieuw Oost-Indien, 1724. Sumatra, in vol. v. 



2. William Marsden. History of Sumatra, 3rd edition. London, 1811. 



3. Malayan Miscellanies ; published at the Sumatran Mission Press, at Bencoolen : 



vol. ii. (1822) contains accounts of several joiumeys. 



4. Dr. Jack. On the Geology of Sumatra. Transactions of the Geol. Society, 



new series, vol. i. page 397. 



5. Memoir of the Life and Public Services of Sir Thomas Stamford Baffles. By his 



Widow. London, 1830. Particularly in the Government of Java, 1811-1816, 

 and of Bencoolen and its dependencies, 1817-1824. 



6. L. Horner. De Batoe-eilanden. Tijdschrift voor Nederlandsch Indie. Jaar- 



gang iii. vol. i. p. 313-371. 



7. L. Horner. Beizen over Sumatra. Tijdschrift van het Bataviaansch Genootschap, 



vol. x. pp. 322-373. 



8. S. Miillcr. Gezigten van bergen, kraters, kusten en eilanden van Java, Sumatra 



en straat Sunda. Verhandelingen over de natuurlijke geschiedenis der neder- 

 landsche overzeesche bezittingen, door de leden der Natuurkundige Com- 

 missie. Leyden, 1839-1844, pp. 447-469 (with plates). 



9. F. Junghuhn. Die Battalander auf Sumatra. Berlin, 1847, 2 vols. 



10. F. Junghuhn. Java (German translation, Leipzig, 1852), vol. i. pp. 51, 70-72, 



75-78, 99-106, with seven sections (topography of Sumatra) ; vol. ii.pp. 808- 

 816 (volcanos of Sumatra). 



11. Nicuivenhuizen en v. Rosenberg. Verslag omtrent het eiland Nias. Verhandelin- 



gen van het Bataviaansch Genootschap, vol. xxx. 1863, pp. 1-153. 



12. W. H. de Greve. Het Oembilienkolenveld in de Padangsche Bovenlanden. 



's Gravenhage, 1871. 



13. E. D. M. Verbeek. In the " Jaarboek voor het Mijnwezen in Nederlandsch 



Oost-Indie," vol. iii. and iv. 1874 and 1875, the following momoirs : 

 a. Preliminary report on the Island of Nias. 



