22 Mr. De la Beche on the Lias of the Coast, 



It is unnecessary to trace the oolite more to the eastward^ it being sufficient 

 for my present purpose to show^ that the sands which rest on the lias marl at 

 Down Cliff belong to that stratum. 



The Lias, in the tract about to be described, may be divided into three 

 portions * : the first, and uppermost, consisting principally of beds of marl ; 

 the second, to which the denomination Lias has usually been confined, of thin 

 beds of limestone alternating with clay; and the third, composed chiefly 

 of marl beds immediately incumbent on the red marl or newer-sandstone 

 formation. I shall describe each of these divisions in the order of this enu- 

 meration. 



I. The Upper Lias Marls occupy a large extent of coast, forming the base 

 of Down Chff, the whole of the cliffs beneath the green-sand at Golden Cap, 

 Shorne Cliff, and the greater part of Black Ven. The upper strata of these 

 marls, as exhibited at Down Cliff, contain a considerable quantity of mica ; 

 but this character does not extend any great thickness, for the marls on the 

 beach between the little hamlet of Sea-town and Golden Cap do not con- 

 tain that mineral. Those portions of the marl which have fallen over from 

 above, from the place where these beds come into contact with the green sand 

 at Golden Cap, are also micaceous, being the continuation of the marls at 

 the base of Down Cliff. 



Numerous organic remains are found in the marls on the shore, between 

 Sea-town and the rocky points projecting into the sea under Golden Cap : 

 the most abundant are belemnites, which, though they occur throughout the 

 greater part of the lias formation in the vicinity of Lyme, are nowhere 

 so abundant as in the upper marls. The Ammonites Bechei of Sowerby is 

 alsQ a common fossil in the same situation ; which likewise affords Terebra- 

 tulae, Trochus anglicus, T. imbricatus. Ammonites Grenovii, Pentacrinites 

 subangularis (of Miller), disjointed portions of Pentacrinites Briareus, 

 lignite, the rare remains of an echinite, the bones of Ichthyosaurus tenui- 

 rostris, &c. 



The thickness of the marl exhibited at Golden Cap must be about two 

 hundred feet ; which, placed upon the three hundred feet of marls exposed in 

 the lower part of Black Ven, would give five hundred feet as the probable 

 thickness of this portion of the lias in the vicinity of Lyme : the marly beds 

 at Shorne Cliff and in the upper portion of Black Ven being a continuation of 



* See Conybeare and Phillips, " Outlines," &c. p. 261. 



