BT THE TRESIDENT. 191 



Several species of Mollusca wliicli were previously known as 

 fossil only, and were supposed to be extinct, have lately been 

 dredged by myself and others from the bottom of the Atlantic. 

 Some of these same species had been described and figured by Pro- 

 fessor Seguenza, of Messina, from Pliocene beds in Sicily. I have 

 no doiibt that many more, perhaps all, of such fossil species will 

 be hereafter discovered in a living state by means of deep-sea 

 explorations. 



Some geologists, and especially of late years, have advocated the 

 theory that oceans have continued for an enormously long period to 

 occupy the same areas that they still occupy. Mr. Darwin was, I 

 believe, the first to broach this idea. He says, in the chapter " On 

 the Imperfection of the Geological Record" ('Origin of Species') : 

 " We may infer that where our oceans now extend oceans have ex- 

 tended from the remotest period of which we have any record ; and, 

 ^ou the other hand, that where continents now exist large tracts of 

 land have existed, subjected, no doubt, to great oscillations of 

 level, since the earliest Silurian period." There does not seem 

 to be any fact adduced or reason given for either of the above 

 inferences. 



If the present oceans and continents have remained unchanged 

 since the Silurian period, how can we account for the widespread 

 distribution of fossiliferous formations, Palfeozoic, Mesozoic, Caino- 

 zoic or Tertiary, and Quaternary or Recent, miles in thickness, all 

 over Europe, Asia, Africa, Australasia, and ]S^ew Zealand ? All oceanic 

 islands are of volcanic origin ; but some of them contain Miocene 

 fossils. These formations are chiefly marine, and necessarily imply 

 the presence of oceans in those parts of the globe which are now 

 continents' and dry land. All the "secrets of the deep" will 

 probably never be revealed to man, nor is he likely to know what 

 terrestrial formations underlie the floor of the mid-ocean. 



In my paper " On the Occurrence of Marine Shells of Existing 

 Species at different Heights above the Present Level of the Sea," 

 which was published in tlie ' Quarterly Journal of the Geological 

 Society' for August, 1880, I stated that many existing species of 

 Mollusca which inhabit great depths only are found in a fossil state 

 at considerable heights above the present level of the sea, so as to 

 show an elevation equal to nearly 12,000 feet, and that such eleva- 

 tion must have taken place at a very late and comparatively recent 

 stage of the Tertiary or Post-Tertiary epoch. In the face of facts 

 like this, can we rightly assign to the present oceans that geologically 

 remote antiquity which is claimed for them ? 



