ON THE FORAMINIFERA IN THE CHALK OF THE HEBRIDES. 739 



agencies during past geological epochs, and standing protests against 

 the danger in geological speculations of drawing deductions from 

 negative evidence. In palseontological geology the warning is per- 

 haps scarcely necessary ; for an accidental discovery of fossils has 

 again and again occurred to produce a deep, timely, and salutary 

 impression on the minds of rash theorists ; and it is not perhaps too 

 much to hope that an equal service will be rendered to the cultivators 

 of physical geology by the discovery of these isolated and strangely 

 preserved relics of vast formations in the Scottish Highlands. 



Note on the Foramtnifera and other Organisms in the Chalk of the 

 Hebrides. By Professor T. Rupert Jones, F.R.S., F.G.S. 



[In the examination of specimens of the Cretaceous Rocks of the 

 Hebrides I have been aided by Professors W. Kitchen Parker and 

 T. Rupert Jones ; and the latter has drawn up the following note 

 on the sections which I submitted to him — J. W. J.] 



No. 0, 2. " Siliceous Chalk, Carsaig, W., Isle of Mull,' 7 and No. 

 0. 3. " Siliceous Chalk, Beinn-y-Hattan," are specimens of Inocera- 

 mus-chalk — that is, made up to a great extent of prisms of Inocera- 

 mus-shell. In No. 3 some of these are pyritized. Poraminifera are 

 abundantly present, constituting the matrix in which the prisms are 

 imbedded. Globigerina cretacea is the most abundant ; and others 

 are present, such as Dentalina, Virgulina, Bulimina, Planorbulina. 



No. 0, 3*. " Siliceous ' Chalk,' Carsaig, E., Isle of Mull," and No. 

 0, 4. " Plinty Chalk, Beinn-y-Hattan," are specimens of silicified 

 Globigerina-ohslk. The Poraminifera are much obscured, except 

 here and there ; and Globigerina cretacea is the only Poraminifer easily 

 distinguished. Inoceramus--prismB and Sponge-spicules are obscurely 

 indicated. Sand-grains (quartz) are present. 



The occurrence of Inoceramus-jwisms as important constituents of 

 some kinds of Chalk has long been known. They form a large pro- 

 portion of some strata of the Chalk at Charlton, near Woolwich, and 

 elsewhere along the Inoceramus-zones. 



Such prisms are figured by Prof. W. C. Williamson in his memoir 

 " On some of the Microscopical Objects found in the mud of the 

 Levant," &c. 1847, ' Manchester Lit. & Phil. Soc. Memoirs,' vol. viii. 

 These prisms, figured in pi. iv. figs. 85 and 86, are described as such, 

 and as being abundant in the " Chalk- detritus" (rotten Chalk-marl) 

 of Charing, Kent, at pages 80, 81. 



Prisms of Inoceramus are carefully described and figured in H. 

 Eley's ' Geology in the Garden,' 8vo. 1859, p. 177, pi. i. fig. 1, &c, 

 as abundant in some English Chalk-flints ; and some are apparent 

 in fig. 113, p. 210, of Heer's < Primaeval World of Switzerland,' 1876, 

 illustrating a microscopic section of the glauconitic shales of the 

 Swiss Gault with Inoceramus concentricus. 



No. 0, 4. Siliceous " Chalk, Gribun, Isle of Mull," is probably a 

 Globigerina- chalk; but the Poraminifera are only obscurely indicated; 

 so also are Sponge-spicules and Inoceramus-iprisma. 



