Geological Society of London. 425 



to a group of very large and far-travelled erratics in Llanarmon 

 parish, Denbighshire." By D. Mackintosh, Esq., F.G.S. 



The author, after referring to a number of northern-drift boulders 

 in addition to those he had noticed in a former paper, describes 

 several large felspathic boulders found up to a height of about 

 1750 feet above the sea, on Cefn-y-fedw, N. of Llangollen. He 

 then gives a somewhat detailed account of the drifts in the neigh- 

 bourhood of Corwen, and of some large felspathic boulders, probably 

 from the Arenig mountains, which are generally found on the sur- 

 face, or interposed between the lower Boulder-clay and an upland 

 extension of the middle sand of the plains. The main part of the 

 paper is devoted to an account of the discovery of a numerous group 

 of very large and far-travelled felspathic boulders in the parish of 

 Llanarmon. Denbighshire. The author refers particularly to a re- 

 markable slickensided boulder, and to the great " Immovable Stone" 

 at Maendigychwyn (now called Eryrys), about 1150 feet above the 

 sea, which is the largest far-trans]3orted boulder he has heard of in 

 the British Isles. He stated a number of facts and considerations 

 which led him to believe that the Llanarmon boulders, along with 

 those further N. and W., must have come all the way from Snowdon, 

 and that they were floated over passes or cols in the intervening 

 ranges of hills by icebergs or coast-ice about the close of the Lower 

 Boulder-clay period. He concluded by noticing the necessity for a 

 personal examination of boulders, instead of relying on answers to 

 queries, and stated that about Llanarmon the felspathic boulders are 

 called " gaanite tumblers," while in Cheshire all kinds of boulders 

 are called "marble stones." 



6. " Note on the Bingera Diamond-fields." By Archibald Liver- 

 sidge, Esq., E.G.S. 



The author commenced by describing the general characters of 

 the older Australian Diamond-field of the Mudgee or Cudgegong 

 District. The Bingera Diamond-field is situated in a basin among 

 the mountains of the Drummond Eange, the encircling hills being of 

 Carboniferous or Devonian age. The diamantiferous drift occurs in 

 patches in the basin, which is invaded by spurs of basalt. The rock 

 under the drift is an argillaceous shale, and here and there are out- 

 crops of a siliceous conglomerate. The diamonds have hitherto 

 been worked only at the surface. The author mentions the principal 

 minerals found associated with the diamonds, which are generally 

 small, and their crystalline forms not very well developed. He also 

 remarks on the general accordance in the geological constitution of 

 various diamantiferous districts. 



7. " Eemarks on the Working of the Molar Teeth of the Dipro- 

 todon." By Gerard Krefft, Esq., F.L.S. Communicated by the 

 President. 



In this paper the author criticized a figure of the lower molars of 

 Diprotodon, published by Professor Owen, on the ground that the 

 teeth are represented in it in an unabraded state, and stated that 

 when the last tooth breaks through the gum, the first of the series is 



