ON THE GEOLOGY OF BAKEABOS. 225 



physical conditions of the region, and they are in accord with all the 

 other available evidence. AVhen the upheaval which set in during 

 Pleistocene time had finally shut out the Pacific waters, Atlantic 

 types gained the mastery in the Caribbean Sea and have to a large 

 extent replaced the older Antilleo-Pacific fauna. ^ 



Disciissio:n". 



The Cfaieman said that, since the late Dr. Brady wrote on the 

 " so-called Soapstone of Piji," there had been no communication on 

 the subject of oceanic deposits of such importance as Mr. Jukes- 

 Browne and Prof. Harrison's paper, which dealt with them from 

 a physical, chemical, and biological point of view. In both cases 

 the deposits were held to be of late Tertiary age, and this conclusion 

 made the excessive depths at which the Barbados earths were 

 supposed to have been deposited all the more startling. Possibly 

 the species of ArcJiceopneustes described by Mr. Gre^^'ory might point 

 to shallower waters. 



Dr. Blanpokd regretted that a diagram-map of the West Indies 

 had not been hung in the meeting-room. He asked for farther 

 evidence as to the red clay being a deep-sea deposit. The mamma- 

 lian fauna of South America, as he had pointed out on a previous 

 occasion, could not be explained unless North and South America 

 had been united at times during the Tertiary era. Turning from 

 these minor points he congratulated the Authors on having conclu- 

 sively answered the challenge thrown down to geologists some years 

 ago, to produce true deep-sea deposits that had been raised above 

 the sea-level. If it was urged that Barbados was on the edge of 

 the oceanic area, the same remark would assuredly not apply to 

 Jamaica. The discovery in Barbados of both Glohigerina- and 

 radiolarian ooze intercalated between shallow-water deposits was 

 clear evidence that portions of the continental area might be de- 

 pressed to oceanic depths and re-elevated. 



Prof. SoLLAs congratulated the Authors on the strength of their 

 case. It could no longer be put forward as an assured fact that deep- 

 sea deposits never enter into the constitution of land-masses. Still, 

 the evidence of the excessive depths claimed by the Authors did not 

 amount to demonstration ; it was of the nature of analogy, which 

 was sometimes misleading. It was to be hoped that additional 

 fossils of the Metazoa would be discovered in the chalky beds. A 

 vastly larger number of observations are required to define the 

 bathymetrical limits of a species or group than in many cases we at 

 present possess. Striking exceptions to general rules are numerous 

 enough to give us pause ; even so characteristically a deep-water 



^ For confirmation of the extent to which the faunae of the Pacific and 

 Caribbean waters still resemble one another, see, as regards moUusca, P. P. 

 Carpenter, Brit. Assoc. Kept, for 1856, p. 363 : as regards echinoderms, Verrill 

 and A, Agassiz, quoted by Sir Wyville Thomson, 'Depths of the Sea,' p. 13 ; and 

 as regards deep-water animals, letters on ' Dredging Operations off the West 

 Coast of Central America,' Bull. Mus. Comp. Zool. vol. xxi., Cambridge, U.S., 

 reprinted in ' Nature,' Jan. 21st, 1892. 



