22 S. V. Wood, Jan. — Sequence of Glacial Beds. 



and Muvio-marine Crag, in the Chillesford bed, and in the Lower 

 Glacial it swarms. In the Middle Glacial it appears to be not 

 uncommon, and at Bridlington it seems, from Dr. Woodward's list, 

 to have occurred. 



Let us now contrast with these features those afforded by the 

 fauna from Moel Tryfaen, and from the Macclesfield sands, given by 

 Mr. Darbishire,^ and that from Kelsea Hill (bed c), given by Messrs. 

 Prestwich and Jeffreys.^ 



Mr. Darbishire, grouping Moel Tryfaen and Macclesfield together, 

 enumerated seventy forms of Marine Mollusca, among which are no 

 less than seventeen or eighteen not known to the Upper Crag, of 

 which only six are Arctic shells ; and these (unlike the principal 

 part of the Bridlington introductions, which are exclusively Arctic) 

 are British forms extending into Arctic seas. The rest of the seven- 

 teen or eighteen are British and Southern. The six British and 

 Arctic forms, however, do occur at Bridlington. 



Of the forty forms (exclusive of the fresh-water Cyrena, but 

 inclusive of the sinistral variety of Fusus antiquus as a separate 

 form and all marine) given by Messrs. Prestwich and Jeffreys from 

 Kelsea Hill, there are six that do not occur in the Crag, only one of 

 which, the never-failing Tellina £altJiica, is British and Arctic, the 

 remaining five being British and Southern ; all are living forms, and 

 there is little, indeed nothing, in the group of shells as a whole that 

 points to any affinity between them and the Bridlington fauna. 

 Comparing it with Mr. Darbishire's list, there also appears an equal 

 want of such a reasonable identity as would justify its reference to 

 the epoch, whatever it be, marked by Mr. Darbishire's list, besides 

 the indication, afforded by the occurrence in profusion of Cyrena 

 fluminalis, of how shallow and estuarine must have been the place of 

 its occurrence, while the exclusively marine fauna of Mr. Darbishire's 

 list occurs at elevations reaching to 1350 feet above Kelsea Hill. 

 Out of the seventy of Mr, Darbishire's list thirty-nine are not known 

 at Kelsea, while out of the forty Kelsea shells of the list of Messrs. 

 Prestwich and Jeffreys there are (exclusive of the Cyrena) nine not 

 in Mr. Darbishire's list. 



In none of these lists does the name of Tellina ohliqiia appear ; 

 and were it not for an imperfect specimen I found at Kelsea, that 

 resembles this shell (but which may nevertheless be, and I think is, 

 only a large and broken T. Balthica), I should have had no hesitation 

 in saying that Tellina ohliqua seems to have died out between the 

 period of Bridlington and that of Moel Tryfaen. 



In the next number, I shall endeavour to show how the physical 

 evidence accords with that deduced from the organic remains. 



1 Geol. Mag., Vol. II., p. 298. * Quart. Journ. Geol. Soc, vol. xvii., p. 448. 



( To be concluded in our next number.) 



