Geological Society of London. 285 



shales, and the whole mass of the limestones seems to be replaced 

 by slates between the Yealmpton and Totnes areas. 



The commencement of the phase of volcanic activity which caused 

 the accumulation of the Ashprington series is shown to coincide with 

 the latest stage of Eifelian deposition, and the Ashprington series 

 may represent continuous or intermittent vulcanicity up to a late 

 stage in the Upper Devonian. North of Stoke Gabriel a mass of 

 limestone seems to have been formed contemporaneously with the 

 voloanic material on the immediate borders of which it occurs. 

 Elsewhei-e the limestones are interrupted by local influxes of volcanic 

 material. The occurrence of other local developments of Middle 

 and Upper Devonian volcanic rocks is described. 



The relationship of the Middle and Upper Devonian deposits 

 varies. In some cases Upper Devonian shales may have been 

 deposited against Middle Devonian limestones ; in others there is 

 a continuous development of limestone, the Middle Devonian lime- 

 stones being succeeded by Cuboides-beds, Goniati te-limestones, and 

 Knollenkalk. The local variations of these are described, and fossil- 

 lists given. The Knollenkalk is shown to pass under Entomis- 

 bearing beds (" Cypridinen-Schiefer "), which are described, though 

 a detailed account of their relationship to the Culm-measures is 

 reserved for a future occasion. 



III.— May 14, 1890.— Dr. A. Geikie, F.E.S., President, in the 

 Chair. — The following communications were read : — 



1. " The so-called Upper-Lias Clay of Down Cliffs." By S. S. 

 Buckman, Esq., F.G.S. 



The blue clay of Down Cliff, Dorset, which has been referred to 

 the Upper Lias, has yielded Ammonites of the genus Dumortieria 

 to the author, notably D. radians. This blue clay is below the 

 Yeovil Sands ; but the position of B. radians in the Cotteswolds is 

 in the limestone above the Cotteswold Sands, which has been placed 

 in the Inferior-Oolite series. 



The author, by combining the Down-Cliffs and Chideock-Hill 

 sections, obtains a sequence of beds from the Middle Lias to the top 

 beds of the Inferior Oolite, including the zones of spinaturn, commune 

 and falciferum, jurense, opalinum, Miirchisones, concavum, and Par- 

 Tcinsoni. 



The genus Dumortieria binds the opalinum- and jurense- zones 

 together; while at Symondsbury Hill the author has found Ludwigia 

 Murchisonce and Lioceras opalinum in the same bed, which renders 

 it difficult to draw a line of demarcation between Lias and Oolite 

 at the top of the opalinum-zone. 



The facts adduced in the paper furnish additional evidence of the 

 unreliability of a grouping which depends upon lithological appear- 

 ances, and it was because no satisfactory line could be drawn between 

 Lias and Oolite that the author, in a previous paper, supported the 

 continental plan of grouping Upper Lias and part of the Inferior 



