Geological Society of London. 43 



follows : — Like Prof. Hull, he distinguished a triple division of the 

 deposits under consideration. 1. The Lower Boulder-clay, or, as he 

 preferred to call it. Lower Glacial Drift, resting immediately upon 

 the eroded surface of the Keuper, consists for the most part of com- 

 pact clay, containing numerous and large striated erratics, together 

 with a fauna of Scandinavian type, the Gasteropoda being generally 

 filled with fine silt containing Microzoa. The author believed that 

 the shells found in this deposit were principally distributed by 

 ground-ice, which took them up and floated them off the shore. 2. 

 The Middle Sands and Gravels, or Interglacial Drift of the author, 

 consist chiefly of sands and gravels containing few (if any) glaciated 

 stones. The fauna of this division is Celtic, with a few Scandina- 

 vian species derived from the Lower Boulder-clay ; the shells were 

 distributed principally by currents ; and the Gasteropoda seldom, if 

 ever, filled with sand containing Microzoa. 3. The Upper Boulder- 

 clay or Upper Glacial Drift, is composed for the most part of clay 

 not so compact as the Lower Boulder-clay, and containing fewer and 

 smaller glaciated stones, which are more abundant near the base. 

 The fauna is Scandinavian at the base of the beds. The shells were 

 distributed principally by ground-ice, and those of southern type 

 derived from the Middle Sands and Gravels. The Gasteropoda are 

 chiefly filled with silt containing Microzoa. The paper was accom- 

 panied by lists and tables of fossils, a large collection of which was 

 exhibited in illustration of the paper. 



2. " The Moffat Series." By C. Lapworth, Esq., F.G.S. 



The fossils found in the highly convoluted Lower Silurian rocks 

 of the southern uplands of Scotland are usually restricted to certain 

 narrow bands of black carbonaceous and Graptolitic shales, which, 

 from their especial abundance in the neighbourhood of the town of 

 Moffat, Dumfriesshire, are known to geologists as the Moffat Shales 

 or Moffat Series. 



The most perfect section of the black shales visible within the 

 Moffat area is exhibited in the cliffs of the gorge of Dobb's Linn, at 

 the head of Moffatdale. It was shown by the author that they are 

 here disposed in a broken and partially inverted anticlinal, which 

 throws off on both sides the basal beds of the surrounding non- 

 fossiliferous greywackes. They are distinctly arranged in three suc- 

 cessive groups or divisions. Each of these divisions is distinguished 

 by special lithological characteristics, and possesses a distinct fauna. 

 To the lower and middle divisions a few fossils are common, but 

 between the middle and upper divisions the palseontological break is 

 complete. These divisions, again, are naturally subdivided info 

 several zones, each characterized by special species, or groups of 

 species. 



A larger exposure of the same deposits occurs at Craigmichan, a 

 few miles to the south-west, where the beds of the lower division 

 are shown to a much greater depth than at Dobb's Linn. In these 

 two localities the general succession of the Graptolitic shales is as 

 follows : — 



