196 NEWER PLIOCENE STKATA OF ENGLAND. [Or. XIIL 



Newer Pliocene strata of the Upper Val d , Ar?io. — When we ascend 

 the Arno for about ten miles above Florence, we arrive at a deep nar- 

 row valley called the Upper Yal d'Arno, which appears once to have 

 been a lake at a time when the valley below Florence was an arm of 

 the sea. The horizontal lacustrine strata of this upper basin are 12 

 miles long and 2 broad. The depression which they fill has been ex- 

 cavated out of Eocene and Cretaceous rocks, which form everywhere 

 the sides of the valley in highly inclined stratification. The thick- 

 ness of the more modern and unconformable beds is about 750 feet, 

 of which the upper 200 feet consist of Newer Pliocene strata, while 

 the lower are Older Pliocene. The newer series are made up of sands 

 and a conglomerate called "sansino." Among the imbedded fossil 

 mammalia are Mastodon arvernensis, ElepTias meridionalis, Bhinoceros 

 etruscus, Hippopotamus major, and remains of the genera bear, 

 hyaena, and felis. 



In the same upper strata are found, according to M. Gaudin, the 

 leaves and cones of Glyptostrobus europams, a plant closely allied to 

 G. heterophyllus, now inhabiting the north of China and Japan. 

 This conifer had a wide range in time, having been traced back 

 to the Lower Miocene strata of Switzerland — and being common 

 at (Eningen in the Upper Miocene, as we shall see in the sequel, 

 Chapter XV. 



Newer Pliocene strata of England. — It is in the counties of Nor- 

 folk, Suffolk, and Essex, that we obtain our most valuable information 

 respecting the British Pliocene strata, whether newer or older. They 

 have obtained in those counties the provincial name of " Crag," ap- 

 plied particularly to masses of shelly sand which have long been used 

 in agriculture to fertilize soils deficient in calcareous matter. 



In Suffolk the strata so named are divisible into the Lower, called 

 the White, or Coralline, and the Upper, or the Red Crag ; * but the 

 inferior division occupies a very limited area, and the Red Crag usu- 

 ally reposes directly and without the intervention of the Coralline on 

 older strata, as in Essex, for example, where the relative position of 

 the Red Crag to the London Clay (an Eocene deposit) and to the 



to pass into a new and distinct species. In my recent work on the Geological Evi- 

 dences of the Antiquity of Man, I have shown (chaps, xxi. to xxiv.) that Mr. Dar- 

 win's theory of natural selection removes many of the principal difficulties which 

 stood in the way of Lamarck's doctrine of transmutation ; and had I inclined as 

 much in 1833 toward embracing Mr. Darwin's views as I do now, I should have 

 expressed myself somewhat differently. But I have thought it best not to recast a 

 passage which has been so often cited, both by writers who opposed and approved 

 of it. The main proposition which seemed so startling in 1833, namely, that spe- 

 cies in general may be older than the lands and seas they inhabit, is now the creed 

 of almost every geologist, whether he adopts or rejects the theory that species may 

 be indefinitely modified in their organization under the influence of new conditions 

 in the animate and inanimate world. 



* See paper by E. Charleswortb, Esq. ; London and Ed. Phil. Mag., No. xxxviii. 

 p. 81, Aug. 1835. 



