760 THE PLIOCENE DEPOSITS OE HOLLAND. [Nov. 1 896. 



change in the molhisca of both deposits, namely, the gradual dying-out 

 of older and soiithern forms and the gradual appearance of northern 

 and more recent species. The evidence which we possess from the 

 Dutch beds is, it is true, at present but small, and, so far as it is 

 negative, it cannot be regarded as of great value. As to the positive 

 evidence, the occurrence of certain species at certain depths, the case 

 is different, and we may draw our conclusions from it with more con- 

 fidence. It may perhaps be urged that the total number of species 

 (about 150) is insufficient to form a representative collection of the 

 mollusca living in these seas during the Pliocene epoch, but if the 

 view I have elsewhere taken, that the general facies of the fauna of 

 any bed must be gained from the species which occur abundantly in 

 it, rather than from all which can be discovered, 1 these shells may 

 have more value than at first appears. The chances are that it is 

 the characteristic forms which have been met with, and it is worthy 

 of notice that the fauna of each horizon has a distinctive and 

 probably a representative character. 



The section (fig. 4) illustrating the views now held is drawn 

 to scale from Cassel, a small town in French Flanders, 27 miles 

 N.W. of Lille, to Amsterdam, a distance of about 150 miles. At 

 Cassel, Diestien beds are found, resting on Eocene strata (Asschien), 

 capping the summit of a hill 515 feet above the sea-level. Passing 

 thence to the N.E., we find, at Ostend, Eocene beds covered by 

 120 feet of recent and Pleistocene deposits, the latter containing 

 Cyrena fluminalis, 2 a freshwater and southern shell which occurs 

 occasionally in the Upper Crag, but which is very characteristic of 

 one of the English post-Glacial horizons. No Diestien beds are 

 present at Ostend, nor was Cyrena fluminalis detected in any of the 

 Dutch borings. 3 



Still farther to the N.E., at Goes, in South Beveland, Scaldisien 

 strata were reached at 114 feet, and Diestien at 183 feet below 

 Ordnance-datum, at about which depth 20 species of echinodermata 

 and polyzoa, and 35 species of mollusca, all characteristic forms of 

 the Coralline Crag, were obtained. Oligocene deposits (Pupelien) 

 were found at 304 feet, showing the Diestien to be 121 feet in 

 thickness. Between 94 and 114 feet, a bed was observed containing 

 Cardium groenlandicum, which Dr. Lorie regards as Pleistocene, but 

 I suggest that it may be the equivalent of those which attain 

 so great a thickness in the other borings, and, 1 believe, represent 

 an upper division of the English Crag. Dr. Lorie states that at 

 Goes no satisfactory division can be made on lithological grounds 

 between the Pliocene and what he regards as Pleistocene deposits. 



In the boring at Gorkum, or Goringhem, about 50 miles E.N.E. 

 of Goes, the Diestien was not reached, even at a depth of 586 feet. 

 Between 293 and 382 feet a bed was met with containing land and 



1 Geol. Mag. 1896, p. 27. 



2 Dollfus, Mem. Soc. Koy. Malacolog. Belg. vol. xix. (1884). 



3 I am informed by M. Mourlon that Cyrena fluminalis is found at all levels 

 in the Flandrien (Upper Pleistocene) of Belgium, deposits which have been 

 proved by boring to be in places 150 feet thick. 



