LOWER GREENSAND. 423 



beds (including gault) and the somewhat perplexing groups between 

 that stratum and the well-defined Kimmeridge clay. These groups 

 are perplexing from their irregular and unequal distribution, both 

 as to area and level, and from the almost continual change of 

 mineral character. In the Portland rock, however, the organic 

 remains are of a clear and nearly uniform and truly oolitic type ; 

 the Shotover sands interpose a truly estuarine or fresh- water series ; 

 and the other sandy and conglomerate masses, which we collect 

 under the title of lower greensand, distinguish themselves from 

 both by a large number of quite different fossils of a cretaceous 

 aspect. 



Originally unequal and irregular in distribution as a floor of 

 the gault, the lower greensand deposits have since been cut up 

 at the surface into detached pieces, usually forming rather con- 

 spicuous tops of hills; and these, when carefully compared, offer, 

 even in a limited space of country, obvious differences ; some tracts 

 being richly fossiliferous, others devoid of them ; some being 

 chloritic sand, others ferruginous sand, others shelly or pebbly 

 conglomerate. 



It will be sufficient for our purpose to take those tracts where 

 the characters of deposition and the facts of organic life are well 

 pronounced; such as Seend in Wiltshire, Faringdon in Berkshire, 

 and the country about Culham and Nuneham in Oxfordshire. 



We are indebted to Mr. Cunnington of Devizes for an instructive 

 notice of this deposit, with fossils, as it occurs at Seend near 

 Devizes a . 



At Seend, in a road-cutting, the lower greensand was found 

 resting on Kimmeridge clay, well characterized, and in particular 

 having masses of septaria marked by boring shells of the lower 

 greensand age, the shells and the sand remaining in the holes. 



The series in this vicinity consisted of upper greensand, 90 feet, 

 gault, 80 ; and then followed in downward order 



i. Sands above, followed by 2. Irony sandstone; 3. Yellowish 

 sand; 4. Irony sandstone, with fossils; 5. Dark green and brown 

 sands; 6. Masses of quartzose gravelly sand and stone, not very 

 ferruginous, but very fossiliferous ; 7. Kimmeridge clay. 



The fossils in the sandy and gravelly beds are marine, and con- 



Geol. Journal, vi. 453 (1850). 



