SEri'EMBER 9, 1010] 



SCIENCE 



333 



advancing ice-sheet. They also claim a 

 derivative origin for the organic contents 

 of the overlying sands and gravels, but 

 some authorities consider the majority to 

 be contemporaneous. Near the western 

 coast of England, shells in much the same 

 state of preservation as those on the pres- 

 ent shores are far from rare in the lower 

 clay, where they are associated with nu- 

 merous striated stones, often closely re- 

 sembling those which have traveled be- 

 neath a glacier, both from the Lake District 

 and the less distant Trias. Shells are also 

 found in the overlying sands up the valleys 

 of the Dee and Severn, at occasional locali- 

 ties, even as far inland as Bridgnorth, the 

 heights of the deposits varying from about 

 120 feet to over 500 feet above the sea- 

 level. If we also take account of the upper 

 boulder clay, where it can be distinguished, 

 the list of marine molluscs, ostraeods and 

 foraminifers from these western drifts is a 

 rather long one.-^ 



Marine shells, however, on the western 

 side of England, are not restricted to the 

 lowlands. Three instances, all occurring 

 over 1,000 feet above sea-level, claim more 

 than a passing mention. At Macclesfield, 

 almost thirty miles in a straight line from 

 the head of the estuary of the Mersey, 

 boulder clays associated with stratified 

 gravels and sands have been described by 

 several observers.-* 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 

 =^W. Shone, Quart. Jaurn. Geol. Soc, XXXIV., 

 1878, p. 383. 



-'Memoirs of the Geological Survey: "Country 

 aro-untl Macclesfield," T. I. Pocoek, 1906, p. 85. 

 Tor some notes on Moel Tryfaen and the altitudes 

 of other localities at which marine organisms have 

 been found see J. Gwyn Jeffreys, Quart. Journ. 

 Geol. Soc., XXXVI., 1880, p. 3.51. For the occur- 

 rence of such remains in the Vale of Clwyd see 

 a paper by T. McK. Hughes in Proc. Chester Soc. 

 of Xat. Hist., 1884. 



shells, some of which are in good condition, 

 have been obtained at various elevations, 

 the highest being about 1,200 feet above 

 sea-level. About forty-eight species of mol- 

 luscs have been recognized, and the fauna, 

 with a few exceptions, more arctic in char- 

 acter and now foirnd 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-' shows, the bivalves are 

 generally broken, but a fair number of the 

 univalves are tolerably perfect. The de- 

 posit 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, biit 

 the majority from Wales, the last being the 

 more angular. Here and there, a block, 

 sometimes exceeding a foot in diameter and 

 usuallj^ 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 lanequal wearing of the ma- 

 terials, the Gloppa deposit diffei-s from 

 most gravels that I have seen. Its situa- 

 tion also is peculiar. It is on the flattened 

 top of a rocky spur from higher hills, which 

 falls rather steeply to the Shropshire low- 



" Xow deposited in the Oswestry iluseum. 



