SCIENCE-GOSSIP. 



63 



Exogyra 



Bed. 



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U 



Ci ackers. 



although there is evidence of a break below the 

 Carstone, which again appears always to pass up 

 into the Gault. The total thickness of the Lower 

 Greensand, as shown above (about 800 

 feet in ChaleBay and 600 feet in Sandown 

 Bay), when compared with that of the 

 equivalents on the mainland (in Surrey 

 about 300 feet), shows a sea opening to 

 the south, that being further indicated 

 by the lithological character of the de- 

 posits and by the fossils. In this the 

 Lower Greensand sea differs considerably 

 from the succeeding Gault, cum Upper 

 Greensand sea (for which we require 

 a distinctive name), since the latter had 

 certainly an easterly aspect, probably a 

 north-easterly one. As the one sea 

 followed the other in time, some slight 

 mingling of the two faunas was to be 

 expected, at the same time it will be 

 found that these are, on the whole, just 

 as distinct as the different conditions 

 would suggest. The flora of the adjoin- 

 ing land, however, does not appear to 

 have .undergone material change. The 

 Lower Greensand of the Isle of Wight 

 is best exposed in Chale Bay ; the 

 accompanying section (fig. 1) will be 

 found of great assistance in identifying 

 the different horizons. The beds are 

 generally fossiliferous, and good speci- 

 mens may be obtained without difficulty. 

 To the south of Shanklin, also, fossils 

 occur plentifully, but at Redcliff and 

 Sandown they are extremely scarce. 

 There are a large number of species 

 recorded, perhaps the following may be 

 considered the more typical : Pseudo- 

 diadema Fittoui, Meycria vectensis, Rhyncho- 

 nella Gibbsiana, R. depressa, Terebratula sella, 

 Exogyra sinuata, Gervillia anceps, Pecten 

 orbicularis, Pcma Mulleti, Panopcea plicata, 

 Thetis Sowerbii, Aporrhais Fittoui, A mmonitcs 

 Dcshaycsii, Am. Hambrovii, and Crioceras Perna Bed 

 Bowerhankii. 



The Gault is not usually fossiliferous 

 in the Isle of Wight, although the whole ^ a 



of it would appear to be present, since 

 Ammonites intcrruptus, typical of the lowest 

 zone, has been recorded. The thickness 

 is given at 139 feet in Compton Bay, 

 146 feet at Blackgang, and 120 feet south 

 of Redcliff, at all of which places the 

 beds may be seen. 



The Upper Greensand belongs really 

 to the same series as the Gault ; the two 

 sets of beds contain the same fossils, only the 

 strong conservative instincts of modern geologists 

 maintain the confusion caused by the continued 





Wealden. 



CU 



u 



use of the two names. On the mainland sandy 

 conditions chiefly obtain to the west, showing 

 the direction in which the land of the period 



<! 



Atlierficld 

 Clay. 



o V» 



//.-: 



Carstone. 



Walpen Sands 

 and Clays. 



Crioceras Beds. 



q 



a 2 



lay, whilst clayey conditions preponderate to 

 the east. In the Isle of Wight the Chert Beds, 

 which form the picturesque crags overhanging 



