78 report — 1865. 



have been found in the drift many miles from their source, and in positions which 

 they could only attain by ascending a considerable slope of the Hope mountain. 



The sudden termination of the moraine mounds in a wide plain of drift, extend- 

 ing towards the present estuary of the Dee, and the general uniformity of level at 

 which this occurs, were pointed out as marking the limit of the sea at the[epoch of 

 this glacier's greatest extension. Some mounds of drift upon this plain, apparently 

 formed by the melting of icebergs in shallow water, were described ; and the general 

 phenomenon of the drift of this district was suggested as well worthy of careful 

 study, in reference to the debated questions relative to icebergs versus glaciers, and 

 the limits of their respective operations. 



The paper is preliminary. The author announced his intention of pursuing the 

 investigations further, especially to the southward and the westward ol the ground 

 already described. 



On some Vegetable Deposits in the Aaehensee. 

 By W. Mattietj Williams, F.C.S. 



The Aaehensee, about thirty miles N.E. of Innspruck, is a very clear lake, with 

 precipitous and richly-wooded banks. At the bottom of this lake the author 

 observed an extensive deposit of trunks and branches of trees, evidently washed by 

 storms into the lake. Many of these were standing upright, with roots attached 

 and partially buried. They had assumed this position from having been washed 

 down into the lake with some soil or stones still adhering to their roots. It was 

 inferred from this that the upright position of fossil trees, even when the roots 

 remained attached, does not necessarily prove that they have grown on the spot 

 where they are found. 



On examination of some of this submerged wood, it was found to be very dark 

 in colour, and so dense that it sunk rapidly in the water. The annual rings 

 separated easily like the layer of an onion, the cambium of each year's growth 

 bavin" - apparently decomposed more readily than the rest of the wood. This was 

 referred to as affording an explanation of the fact, that fossilized wood shows the 

 original structure, even when all the wood has been replaced by mineral matter. 

 The spaces between the rings would be first filled up in cases where deposition is 

 occurring, and then the wood-rings would afterwards be replaced by further 

 deposition as they gradually decomposed, and thus a series of concentric strata be 

 formed. 



Mr. Williams stated many reasons for supposing that, at the period of our coal 

 formation, the British Isles had the configuration of an exaggerated Norway, a 

 rid°e or backbone of mountains, with deep wide inlets or fiords, some inland 

 lakes, and many small outlying islands. With such a configuration, and a climate 

 favourable for the rapid growth of any form of ponderous vegetation, the trees 

 growing on the steep banks of the lakes and brackish fiords or estuaries would be 

 continually washed down and settle in these basins, and thus form the coal-seams 

 while the water remained clear. The dark-coloured and striped shales and rock of 

 the coal-measures would be formed wherever the waters were turbid, and a mixture 

 of mineral aud vegetable matter was thus deposited together. 



Mr. Henby Woodward described and exhibited specimens of a new Phyllopo- 

 dous Crustacean from the Moffat shales (Lower Silurian), Dumfriesshire. 



These anthracitic shales abound in the remains of Graptolites, but other fossils 

 are extremely rare. Two Phyllopodous Crustacea have been described from them 

 by Mr. Salter, namely, Pettocaris aptychoides and P. Ilarktiessi. 



The new form closely resembles a Discina, but has a sector of ^th of its arc re- 

 moved in nearly every specimen, the segment being separated from the rest of the 

 disk-shaped shield by a line of suture. The shield is slightly conical, and ornamented 

 with fine concentric lines ; there is no dorsal suture as in P. aptychoides. A specimen 

 from the cabinet of Mr. Carruthers shows the wedge-shaped rostral portion in situ. 



The most perfect example measures 7 lines in diameter. The caudal portion 

 is not preserved. The author proposed for it the generic name of Disanoearis, 



