292 GEOLOGICAL CONTEMPORANEITY ix 



distinct from those now living ; while the far less 

 numerous class of Echinoderms presents three, and 

 the Crustacea two, such orders, though none of these 

 come down later than the Palaeozoic age. Lastly, 

 the Reptilia present the extraordinary and excep- 

 tional phenomenon of as many extinct as existing 

 orders, if not more ; the four mentioned maintain- 

 ing their existence from the Lias to the Chalk 

 inclusive. 



Some years ago one of your Secretaries pointed 

 out another kind of positive palseontological 

 evidence tending towards the same conclusion 

 afforded by the existence of what he termed 

 " persistent types " of vegetable and of animal 

 life. 1 He stated, on the authority of Dr. Hooker, 

 that there are Carboniferous plants which appear 

 to be generically identical with some now living ; 

 that the cone of the Oolitic Araitcaria is hardly 

 distinguishable from that of an existing species ; 

 that a true Pinns appears in the Purbecks and a 

 Juglans in the Chalk ; while, from the Bagshot 

 Sands, a iJanksia, the wood of which is not 

 distinguishable from that of species now living 

 in Australia, had been obtained. 



Turning to the animal kingdom, he affirmed 

 the tabulate corals of the Silurian rocks to be 

 wonderfully like those which now exist ; while 



1 See the abstract of a Lecture ' On the Persistent Types of 

 Animal Life," in the Notices of the Meetings of the Rental 

 Institution of Great Britain. June 3, 1859, vol. iii. p. 151. 



