294 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. ([Apr. 5, 
occurs in the Wenlock limestone of Gliddon Hill. This species in 
some respects resembles the L. pomum of Agassiz, a carboniferous 
limestone fossil. The difference consists m the Silurian specimens 
being larger, having wider ambulacra, and a greater number of plates 
in the interambulacral spaces. The small spines had the same form, 
and the manner of attachment and shape of the plates agree in every 
particular with the carboniferous limestone species. 
3. On Fossil Bones found in the Crac of SurroLK. By Joun 
Wieeins, Esq., F.G.S. 
Tue author states, that near Ramsholt Creek, Sutton, and in other 
parts of Suffolk belonging to the Crag formation, large quantities of 
fossil teeth, bones, and coprolitic substances are found. These re- 
mains are rich in phosphate of lime, and are now collected for agri- 
cultural purposes. They are found mixed with sand and gravel 
from two to four feet below the surface, and about 300 tons had 
been procured from about a rood of ground which had been turned up. 
Apri 5, 1848. 
James McAdam, Esq. and Robert W. Mylne, Esq. were elected 
Fellows of the Society. 
The followmg communications were read :— 
1. Sketch of the Structure of parts of NortH and SoutH WALEs. 
By Professor Ramsay, F.G.S., and W. T. Ave ting, F.G.S. 
[Abstract by the Authors. ] 
THE country to the south and south-east of the Dolgelly and Bala 
district may be briefly described as follows. 
Towards the higher part of the rocks that rest on the Bala lime- 
stone are certain bands of sandstone, of comparatively trifling thick- 
ness, but important as regards the part they play m explaining the 
structure of Wales. They are not continuous, but local and inter- 
mittent, skirting in parts the base of the overlying formations 
through Montgomeryshire and Radnorshire, far down into South 
Wales in Caermarthenshire. Above these sandstones, wherever they 
occur, from the neighbourhood of Dinas Mowddy to Llanddewi- 
ystrad-enny in Radnorshire, are certain slaty shales from 1000 to 
1500 feet thick, and above these thick masses of sandstone (mingled 
with occasional shales), sometimes attaining an aggregate thickness 
of about 2000 feet. These sandstones we believe to be the true 
Caradoc sandstone of Sir Roderick Murchison, bearmg the same 
general relation to the underlymg slates and the overlying Wenlock 
shale that the typical Caradoc sandstone exhibits in Shropshire. The 
contortions in these beds towards the east in Montgomeryshire 
occasionally brmg up the underlying slates. In one instance also the 
Wenlock shale overlies them in a long trough, which is crossed by 
the Mallwyd and Welshpool road at Llangadfan and Llanerfyl. 
Oe SS 
