18 president's address. 



and sands have been described by several observers. 1 The clay stops at 

 about 1,000 feet, but the sands and gravels go on to nearly 1,300 feet, 

 while isolated erratics are found up to about 100 feet higher. Sea shells, 

 some of which are in good condition, have been obtained at various eleva- 

 tions, the highest being about 1,200 feet above sea-level. About forty- 

 eight species of molluscs have been recognised, and the fauna, with a few 

 exceptions, more arctic in character and now found at a greater depth, is 

 one which at the present day lives in a temperate climate at a depth of a 

 few fathoms. 



The shell-bearing gravels at Gloppa, near Oswestry, which are about 

 thirty miles from the head of the Dee estuary, were carefully described 

 in 1892 by Mr. A. C. Nicholson. He has enumerated fully sixty 

 species, of which, however, many are rare. As his collection 2 shows, 

 the bivalves are generally broken, but a fair number of the univalves 

 are tolerably perfect. The deposit itself consists of alternating seams 

 of sand and gravel, the one generally about an inch in thickness, the 

 other varying from a few inches to a foot. The difference in the 

 amount of rounding shown by the stones is a noteworthy feature. 

 They are not seldom striated; some have come from Scotland, others 

 from the Lake District, but the majority from Wales, the last being 

 the more angular. Here and there a block, sometimes exceeding a 

 foot in diameter and usually from the last-named country, has been 

 dropped among the smaller material, most of which ranges in diameter 

 from half an inch to an inch and a half. The beds in one or two places 

 show contortions ; but as a rule, though slightly wavy and with a gentle 

 dip rather to the west of south, they are uniformly deposited. In this 

 respect, and in the unequal wearing of the materials, the Gloppa 

 deposit differs from most gravels that I have seen. Its situation also 

 is peculiar, It is on the flattened top of a rocky spur from higher hills, 

 which falls rather steeply to the Shropshire lowland on the eastern 

 side, and on the more western is defined by a small valley which 

 enlarges gradually as- it descends towards the Severn. If the country 

 were gradually depressed for nearly 1,200 feet, this upland would 

 become, first a promontory, then an island, and finally a shoal. 



The third instance, on Moel Tryfaen in Carnarvonshire, was care- 

 fully investigated and described by a Committee of this Association 3 

 about ten years ago. The shells occur in an irregularly stratified sand 

 and gravel, resting on slate and overlain by a boulder clay, no great 



1 Memoirs of the Geological Survey : ' Country around Macclesfield,' T. I. Pocock 

 (1906), p. 85. JFor some notes on Moel Tryfaen and the altitudes of other localities 

 at which marine organisms have been found see J. Gwyn Jeffreys, Quart. Joum. Oeol. 

 Soc, xxxvi. (1880), p. 351. For the occurrence of such remains in the Vale of Clwyd 

 see a paper by T. McK. Hughes in Proc. Cliester Soc. of Nat. Hist., 1884. 



* Now deposited in the Oswestry Museum. 



8 Brit. Assoc. Report, 1899 (1900), pp. 414-423. 



