128 PROF. W. BOYD DAWKINS ON A PLIOCENE [May I903, 



Suffolk, and Essex. It is proved, by the presence of the northern 

 mollusca, to have been continuous with the Arctic Sea, and by the 

 angular and sharp-edged flints, observed by Lyell in the Red Crag, 

 to have been occupied sometimes by floating ice. The rivers opening 

 into it carried down materials which were derived, as the late 

 Sir Joseph Prestwich and Mr. Jukes-Browne 1 pointed out, from 

 the west. A drainage-area of Carboniferous Limestone, Lias, and 

 Chalk contributed to the materials forming the Eed Crag. In the 

 Red Crag of Sutton the Oolite and the Lower Greensand also are 

 represented. 2 



In other words, the rivers flowed eastward from the Carboniferous 

 rocks of the Pennine Chain and its southerly continuation, through 

 Charnwood Eorest, and had drainage-areas similar to those of the 

 rivers thrown off westward from that axis. 



The depression of the area of the North Sea, which allowed the 

 Arctic mollusca to migrate as far south as Essex, renders it probable 

 that the ancient barrier of land, in the Eocene (Oligocene) and 

 Miocene Periods, which extended from the North of Scotland to 

 Iceland and Greenland, was submerged, and that the waters of the 

 Atlantic were in free communication with those of the Arctic Sea west 

 and north of the line of sharp depression marked by the 100-fathom 

 line, rapidly descending to depths of more than 1000 fathoms. The 

 absence of marine deposits of Upper Pliocene age on the western 

 side of Britain may be accounted for by this low area (now sub- 

 merged) being then the coast-line, and the whole of the rest of the 

 British Isles being dry land, with the main watersheds and river- 

 valleys very much as they are now, although denuded, in the area 

 which still remains above the sea. In this case the western 

 equivalents of the Pliocene Crags in the east would be submerged. 



Under conditions such as these, there would be no physical 

 barrier to the migration of the Upper Pliocene mammalia from 

 Auvergne. over the plains of Erance, and across the valley of 

 the English Channel, into Britain, and, it may be added, into 

 Ireland. The discovery of a few of them in a bone-cave in Derby- 

 shire is to be looked upon as a proof of the range of the whole fauna 

 over the north-western region. Their route northward through 

 Erance is marked by the remains of Elephas meridionalis and 

 Rhinoceros etruscus in the gravel-pits of St. Prest, near Chartres. 3 

 In the South of England one of them (Elephas meridionalis) has 

 been discovered in a gravel-bed at Dewlish in Dorset. 4 With this 

 exception, they have hitherto been found in Britain only at the 

 mouth of the rivers that opened into the North Sea of the Upper 

 Pliocene age. The discovery at Doveholes establishes their presence 

 on the uplands, on the backbone of England, drained by these very 

 rivers. 



1 < Building of the British Isles ' 2nd ed. (1892) p. 358. 



2 Prestwich, Quart. Journ. Geol. Soc. vol. xxvii (1871) p. 476; Jukes-Browne, 

 op. supra cit. p. 357. 



3 I obtained this species of Rhinoceros from the gravel of St. Prest myself. 



4 C. Reid, « Pliocene Deposits of Britain ' Mem. Geol. Surv. (1890) p. 207. 



