AJfred Bell — Post-glacial Drifts of Ireland. 447 



periods. The Flora of the Wealden is characterized by a great 

 abundance of Coniferce, GycadetB, and Ferns, and by the absence of 

 leaves and fruits of Dicotyledonous Angiosperms. Gyrogonites, or 

 spore-vessels of Chara, so plentiful in the Tertiary strata, were 

 found in 1855 in the Hastings Beds of the Isle of Wight. The 

 Miocene Beds of Europe, which have probably their only English 

 equivalents at Bovey Tracey in Devonshire, present a vegetation 

 differing little from that of the present day. The plants of the 

 submerged forests of our coasts at Cromer, Torquay, and elsewhere, 

 contain identical species with those now growing in England. 



From what has been already brought before our notice it is 

 clear that Araucarias, Pines, Cycads, Zamias, and other exogenous 

 plants now growing, have their generic representatives as early as 

 the Secondary epoch. The persistence of a species tlirough more 

 than one geological period can seldom be traced ; gaps intervene, 

 and it is only indirectly that the changes which have taken place 

 on the earth's surface can be determined, the evidences being too 

 frequently rendered obscure by the superincumbent beds, or placed 

 altogether beyond our reach in the depths of the sea. The fact that 

 the Cretaceous beds of Dorsetshire rest unconformably on the beds 

 below shows that a great interval of time elapsed between the 

 deposition of the two series, and accounts for the dissimilarity of 

 their Faunas. There are instances, however, where the chain of 

 life is unbroken, and uninterruptedly carried on, although accom- 

 panied by the continual appearance of new forms. 



Note. — The Geology of the County of Dorset is illustrated by the following works 

 published by the Geological Survey of England. Maps on a scale of one inch to a 

 mile, Sheets, 15, 16, 17, 18, 21, 22. Horizontal Sections, Sheets 19, 20, 21, 22, 

 and 56. Vertical Sections, Sheet 22. 



Erkatum. — In the first part of this paper, which appeared in our September 

 Number, at p. 409. 



Eleven lines from top of page, /or, "are in the £7-itish Museum," read, "are in 

 the Ely Museum." — Edit. Geol. Mag. 



IV. The PALiEONTOLOGY OF THE PoST-GLAOIAL DrTFTS OF IRELAND. 



By Alfred Bell. 



I HAD hoped that ere this some one better acquainted than my- 

 self with Irish post-Tertiary Geology would have collected into 

 one memoir the details scattered throughout the various scien- 

 tific journals, thus enabling English geologists to compare the 

 later deposits of Britain with those of the sister-kingdom. Since 

 no one has done so, I venture to put some notes of my own upon the 

 subject before the readers of the Geological Magazine, especially 

 as, in some recent discussions upon the Irish drift, ■'Palceontological 

 succession" has not received the consideration it may faii'ly claim. 



Formations in different localities, producing groups of fossils 

 which, if not exactly the same, taken species by species are so in 

 their general aspect, may reasonably be considered to be of the same 

 age, since it is rarely if ever the case that the same biological con- 

 ditions return at different periods. It may also be assumed that 

 where formations in two localities contain faunas widely divergent 



