2 CRETACEOUS GROUP. 



Islands, in their stratigraphical order of superposition, I shall take these as a type of the 

 whole, supplying any deficiency in the series by examples afforded by other localities. 



THE LOWER GREENSAND. 



The Lower Greensand, occupies an extensive tract in the southern part of the Isle of 

 Wight, where it attains a thickness of nearly 900 feet; this great formation has been so 

 carefully examined and well described by the late Dr. Eitton, 1 in his stratigraphical 

 account of the section from Atherfield to Rocken End, on the south-west coast of the 

 island, that 1 must refer the reader for full information te that valuable memoir for further 

 details. Having worked several times over all the beds of that remarkable and most in- 

 structive district, and in my excursions had the advantage of the local knowledge and 

 assistance of Dr. Eitton's collector and guide, 2 I shall now merely attempt a generalized 

 account of this section, for the purpose of pointing out the beds with which we are more 

 immediately interested, in our description of the Echinidse contained therein. 



The entire series of the Lower Greensand beds, 809 feet in thickness, rise in succes- 

 sion from the shore and ascend into the cliffs between Atherfield Point and Rocken End, 

 towards which they dip at an inclination of about 2°. 



The following Subdivision of the Atherfield Section was proposed by Dr. Fitton, in 



ascending order. 



Feet. Inches. 



I. Perna Mulleti Bed 5 3 



II. Atherfield Clay 60 



III. The Cracker Rocks 85 



IV. The Lower Gryphaea Group 32 



V. Scaphites Group 50 4 



VI. Lower Crioceras Group 16 3 



VII. Walpen Clays and Sands 57 



VIII. Upper Crioceras Group 46 2 



IX. Walpen and Ladder Sands 42 



X. Upper Gryphaea Group 16 



XI. Cliff-End Sands 20 



XII. Foliated Clay and Sand 25 



XIIL Sands of Walpen and Black-Gang Undercliff 97 



XIV. Ferruginous Sands of Black-Gang Chine 20 6 



XV. Upper Clays and Sand-Rock 118 



XVI. Various Sands and Clays 118 4 



808 10 



1 " A Stratigraphical Account of the Section from Atherfield to Rocken End, in the South-west Coast of 

 the Isle of Wight," 'Jour, of the Geol. Soc' vol. iii, p. 289, 1847. 



2 Mr. Charles Wheeler, fisherman, at Ventnor, is the person alluded to, he has a most correct know- 

 ledge of the range and position of all the beds, and of their fossil contents, and is a most trustworthy 

 guide to the Atherfield Section. 



