70 A. Bell — Succession of the Later Tertiaries in Gf. Britain. 



On the western side of Britain a different set of conditions 

 obtains in the beds beneath the Till in Kilmaurs, Tangy-Glen, and 

 elsewhere. Of the 22 species recorded, 17 are still British ; but the 

 remaining five are extra-British, new to the fauna, and of tiue 

 northern types corresponding to those on the east coast of Brid- 

 lington and Fife, as will be discussed presently. 



The climax of the Glacial epoch occurs with the Great Chalky 

 Boulder-clay, the true Scottish Till, the drift and unfossiliferous 

 Till of the Midlands and north-west from Lancashire to Shropshire. 

 From the presence of occasional horns, bones, and teeth in the 

 Scottish clays, the remission at times of the intense cold may be 

 inferred, as in the Greenland summer. I have no knowledge of the 

 Crofthead Peat, except from the kindness of Mr. Mahoney, and his 

 and Mr. Geikie's papers in the Geol. Mag. Vol. II. 1869 fbut, con- 

 sidering all the evidence, I am less inclined to regard it as an 

 intercalated deposit in the Lower Till than as occupying a depression 

 at its immediate close, the overlying drifts corresponding more to 

 the higher English Purple Clays than to true Till. The fauna and 

 flora, including Bos primigenius, are certainly not Arctic, as they 

 should be if Greenlandic conditions prevailed. 



The Purple Clays of Yorkshire and Lincolnshire mark the 

 close of the first Glacial epoch in Britain. The researches of 

 Mr. Lamplugh have definitely settled the question as to the fauna 

 of the intercalated masses of sand and clay in the basement 

 beds not being in position. Of the 120 molluscs on record from 

 Bridlington, 1 I find on analysis that 39 are confined to these sands, 

 and of the others, 22 are now extra-British, all of the species being 

 still existing. The age when these molluscs lived would probably 

 be about the time when the Arctic plant-bed was forming on the now 

 Norfolk coast, the Nucula Cobboldice and Tellina obliqua linking it to 

 the Newer Pliocene fauna, their habitat in the deep North Sea not 

 far removed from shore— a few miles perhaps — similar to the Dogger 

 and Antrim turbot banks, where northern forms still exist. Mr. 

 Dawson records a similar deposit about eight miles off Cruden, from 

 whence his dredge always brought up dead shells of northern types ; 

 of the seventeen species recorded, nearly all are found at Bridlington, 

 and like deposits are not uncommon elsewhere. The Bridlington 

 fauna is essentially a deep-sea one, and in no case could have 

 originated or formed in any of the deposits of the Glacial epoch in 

 Britain. 



With the gradual cessation of Arctic conditions, depression began 

 again, lasting until the waves of the Atlantic washed the shores of 

 a coast-line extending in an irregular tract from the Severn to the 

 Tees, accompanied by excessive thermal changes and the inbringing 

 of a new series of life forms. Eliminating all the Bridlington 

 species as of doubtful British origin, and all land and freshwater 

 mollusca on either side from the list of species before and after the 

 major glaciation treated of above, there remain of the Newer 



1 Dr. Jeffreys in working up the list of species in Mr. Lamplugh' s paper omitted 

 any reference to Mr. S. V. Wood's, and many other notices on the fauna. 



