158 8. V. Wood, Jim. — The Post-Olacial Period. 



Spratt has shown to have once probably existed about Malta,' and by 

 ■which intercourse between the two continents was formerly possible, 

 having probably disappeared at the period before alluded to, when 

 the southerly winter migration of the pachydermata was arrested. 

 Now the molluscan associate of the great mammalia in the older 

 Post-glacial deposits of Britain, Cyrena fluminalis, seems to be cut 

 off from Europe and from Northern Asia by nearly the same barriers 

 as those which, confine the great pachydermata, since it ranges at the 

 present day from the Nile, through Syria, to the Himalayas and 

 China ; while, so far as is yet known, this shell has not occurred in 

 this country in association with Eeindeer remains. 



It should not be forgotten, in this question, that the remains of 

 some Coleopterous insects, obtained by Mr. Fisher from an undoubted 

 Post-glacial deposit at Lexden (and from which as yet we have no 

 occurrence of Eeindeer remains), were examined by Mr. T. V. 

 "Wollaston, JF.L.S., who, guarding himself from a decided opinion as 

 to the specific identification of the specimens, states that from two of 

 them (especially a Cossiphus, which he says does not occur north of the 

 Pyrenees) he did not think there could be much doubt that a warmer 

 temperature than at present obtains was indicated by the forms thus 

 procured by Mr. Fisher.^ If Mr. Wollaston's view be correct, it would 

 be only necessary to suppose that this Post-glacial deposit of Lexden 

 preceded others in which the remains of insect groups resembling 

 those of Northern Europe occur. 



3. The Geological evidence resumed. — At Paull Cliff and Kelsea 

 Hill, in Yorkshire, there occurs a gravel, containing, in association 

 with marine shells, this freshwater molluscan associate of the 

 Megarhine Ehinoceros in the Thames Brick-earths, Cyrena fluminalis, 

 which, like its Mammalian associate, inhabited this country in pre- 

 glacial times. This gravel, at one of these localities, is seen to rest 

 on the Glacial-clay, and at the other to be overlain by the non-glacial 

 Boulder-clay of Hessle previously alluded to. The marine mollusca 

 occurring with it, moreover, are clearly Post-glacial, being all of 

 living species, which, with two or three exceptions found in seas 

 immediately to the North, inhabit British seas ; contrasting in this 

 respect with the Glacial-clay on which the gravel reposes, which 

 yields (not far off, at Bridlington) a more arctic fauna, and one con- 

 taining the two well-known Crag species Nucula Cobboldics and Tellina 

 ohliqua, whose nearest living anologues occur in the Pacific. The 

 presence of this fluviatile shell in swarms in this gravel shows that 

 the land had emerged from the glacial sea so as to support a river 

 not far distant ; and the position of the gravel thus overlain by the 

 Hessle-clay, is shown by the coast section to occupy troughs cut out 

 of the deeply-denuded glacial beds. We cannot doubt, therefore, 

 that we have here one of the deposits of the earlier part of the Post- 

 glacial period, similar to the Brick-earths of the Eastern Thames 

 valley, that are full of the same shell ; and that in its overlay by the 

 non-glacial Boulder-clay of Hessle we get evidence of the incoming, 



1 Quart. Journ. Geol. Soc, vol. xxiii., p. 292. 

 * Quart. Journ. Geol. Soc, vol. xix., p. 399. 



