152 Geological Society. 



gravel. He traced the great boulder-bearing clay and gravel around 

 "Wolverhampton eastward through Central England, to where it 

 graduated into the cha]ky clay of Lincolnshire ; and laid great 

 stress on the commingling, at Wolverhampton, in this deposit, of 

 erratics (chiefly granite and felstone) from the north with erratics 

 (chiefly chalk-flints and gryphites) from the east. He described the 

 clay and sand around Gainsborough, Retford, &c. He correlated 

 the " carrion," or lower Boulder-clay of the Yale of York (con- 

 taining Carboniferous, Jurassic, and granitic erratics), with the lower 

 yellowish-brown clay of the Aire and Wharfe valleys and the plain 

 of Craven. He likewise correlated patches of upper clay in the 

 latter areas with the upper Boulder-clay of the Lancashire plain, 

 but was not certain that they were of Hessle age. The solution of 

 the main question depended chiefly on the relative age of the 

 Wolverhampton and Stafford clay-and-gravel, which he was dis- 

 posed to regard as the equivalent of the lower brown Boulder- clay 

 of the N.W. and likewise of the chalky clay of Lincolnshire. He con- 

 cluded by considering facts which might be regarded as opposed to 

 this view, and by giving his reasons for regarding the palseonto- 

 logical evidence of the relative age of deposits as not, in all cases, 

 reliable. 



January 21. — Henry Clifton Sorby, Esq., E.R.S., President, in the 



Chair. 

 The following communications were read : — 



1. " On the Genus Pleur •acanthus, Agass., including the Genera 

 Orthacanthus, Agass. & Goldf., Diplodus, Agass., and Xenacanthus, 

 Beyr." By J. W. Davis, Esq., E.G.S. 



2. "On the Schistose Yolcanic Rocks occurring on the west of 

 Dartmoor, with some Notes on the Structure of the Brent-Tor 

 Volcano." By Prank Rutley, Esq., E.G.S. 



Among the ashy beds of this district are certain amygdaloidal 

 schistose rocks, which the author is of opinion are really lava-flows, 

 which have probably been crushed or infiltrated, and have so as- 

 sumed a foliated structure owing to pressure from superincumbent 

 beds acting on rocks thus constituted. They are much altered, but 

 were probably once basalts. The author considered it very probable 

 that these schistose beds and Brent Tor, considered to be of Car- 

 boniferous age, are identical with beds near Tavistock and in the 

 Saltash district, which are of Upper Devonian age. 



In the concluding part of the paper the author described the beds 

 of alternating ashes and lava, now much disturbed by faults, which 

 constitute all that remains of the ancient Brent-Tor Volcano, and 

 endeavoured, from the evidence which can be thus obtained, to give 

 a probable reconstruction of the former cone. 



3. "On Mammalian Remains and Tre,e-trunks in Quaternary 

 Sands at Reading." By E. B. Poulton, Esq., F.G.S. 



