326 Reports and Proceedings— 
probably of the same age, and this probably is that of the Pebidians of 
St. Davids, to some of which they have, lithologically, a very close 
resemblance. 
III.—June 9, 1880.—Robert Etheridge, Esq., F.R.S., President, in 
the Chair.—The following communications were read :— 
1. ‘‘On the Occurrence of Marine Shells of Existing Species at Dif- 
ferent Heights above the Present Level of the Sea.” By J. Gwyn 
Jeffreys, LL.D., F.R.S., Treas. G.S. 
This paper resulted from the author’s examination of the Mollusca 
procured during the expeditions of H.M. 8S. ‘Lightning’ and ‘ Por- 
cupine’ in the North Atlantic. He stated that he found several 
species of shells living only at depths of not less than between 9000 
and 10,000 feet, which species occurred in a fossil state in Calabria 
and Sicily at heights of more than 2000 feet, such depths and heights 
together exceeding the height of Mount Etna above the present level 
of the Mediterranean. He then gave an account of the Post-Tertiary 
deposits in Europe, Asia, and North America, to show their various 
heights, and especially of the raised beach on Moel Tryfaen in 
Caernarvonshire, which was from 1170 to 1350 feet high. Some of 
the shells in that deposit were boreal and did not now live in the 
adjacent sea. The author stated that no shells of a peculiarly northern 
character had been noticed in the west or south of England. He then 
questioned the permanence and even the antiquity of the present 
oceanic basins, from a consideration not only of the fauna which now 
inhabits the greatest depths, but also of the extent of oscillation which 
had prevailed everywhere since the Tertiary period. A complete list 
of the Moel-Tryfaen fossils was given, to the number of 60, besides 
3 distinct varieties, of which number 11 were arctic or northern, and 
the rest lived in Caermarvon Bay. All of these fossils were more 
or less fragmentary. 
2. “‘On the Pre-Devonian Rocks of Bohemia.” By J. EH. Marr, 
Esq., B.A., F.G.8. 
The author commenced with a brief notice of the Pre-Cambrian 
rocks, which are gneisses and schistose limestone with intrusive 
eclogite; over these lie unconformably green grits, ashes, breccias, 
hornstones (étage A of Barrande), which the author considers to repre- 
sent the Harlech Group of Wales. Etage B is unconformable with 
this, but conformable with C, which contains the “ primordial” 
fauna. D contains the colonies. E to H are Silurian, and more 
calcareous than those underlying them. The base of the group is 
unconformable with those beneath. The lithological characters of the 
various beds were described. The following are the associated igneous 
rocks :—Granite, Quartz-felsite, Porphyrite, Mica-trap, Diabase, 
Diorite, Eclogite. Of these brief descriptions were given. The 
author gave a comparison of the various shales with English deposits. 
The Pre-Cambrian Series much resemble the Dimetian and Pebidian of 
Wales, the latter being étage A; étage B, the Harlech; étage C, the 
Menevian, probably a deep-water deposit, as is indicated by the 
abnormal size of the eyes of its Trilobites; the lowest bed of étage D 
probably represents part of the Lingula Flags of Britain. D, a, 1, 8 
