66 TROCEEBINGS OF THE GEOLOGICAL SOCIETY, 



been suggested that the Graptolite shales of the Silurian system were 

 deposited in deep water, and, so far as the fauna is concerned, the 

 hypothesis appears plausible enough ; but the interstratification of 

 coarse sandstones in places seems a fatal objection. The fine slates 

 and interstratified volcanic tuffs of Silurian and Cambrian age are, 

 however, sometimes of great thickness and extent, and are worth 

 further examination to see if any of them are possibly of deep- 

 water origin*. 



Throughout a large oceanic area at present it is pretty evident 

 that, practically, no deposits are being formed. The fact that teeth 

 of what are believed, on good grounds, to be extinct forms of Shark 

 have been dredged in a corroded state from the bottom of the ocean 

 shows that such objects have lain for ages where no sediment was 

 deposited to entomb them. There is no ground for surprise there- 

 fore if the abyssal red clay is unknown in the older rocks. But the 

 absence of strata corresponding to the Globigerina- and Eadiolarian 

 ooze of the present oceans is, so far as our knowledge extends, in 

 favour of the contention that the continental areas have not been 

 depressed beneath the deep sea. 



At the same time two recent discoveries of deep-sea deposits, 

 each on the border of the continental area, serve to show how 

 cautions we should be in coming to decided conclusions. These 

 two instances are in the Solomon Islandsf, concerning which I shall 

 have some additional remarks to make when dealing with insular 

 faunas, and in Barbadoes J. The evidence in the latter case is very 

 remarkable and peculiarly complete, for the deep-sea Eadiolarian 

 ooze rests upon sandstones and clays with coal, believed to be of 

 older Tertiary age, and which are evidently littoral, estuarine, or flu- 

 viatile in origin. It is clear that the island must have formed part 

 of a continent, that it must have been depressed to a depth of over 

 1000 fathoms, and then re-elevated ; and there is, so far as I under- 

 stand, no question that these changes have taken place within the 

 Tertiary era and probably within the Miocene and Pliocene periods. 

 Barbadoes is at present surrounded on all sides by seas over 1000 



* There is so great a resemblance between some of these remarks and the 

 ■views on the same subject expressed by Dr. Nicholson in the last edition of his 

 ' Manual of Paleontology,' i. p. 75, that it is necessary to explain that all this 

 part of the address was written before I had seen Prof. Nicholson's work, and, 

 I believe, before it was published. 



t Guppy, 'Solomon Islands, Geology,' &c., pp. 77, 81, &c. 



]. Feilden, Ibis, 1889, p. 478 ; Jukes-Browne and Harrison, 'Nature,' vol. xxxix, 

 pp. 367, 607 ; Gregory, Q. J.G. S. xlv. p. 640. 



