Ocean Deposits, Ancient and Modern. 



II. — The Mollusca. 



OF the various forms of animal life abounding off our shores, the 

 most wide-spread, as also the most important, are the Mollusca ; 

 and their general distribution having been well determined, it is 

 possible to compare their extension in our day with their extension in 

 the older stratified deposits. Returning, therefore, to the type more 

 specially selected for comparative purposes in this discussion, viz., 

 the Upper Cretaceous period, several questions at once present them- 

 selves for solution, and may now be taken in order. 



I. Was the moUuscan fauna of that period, in its main features, 

 similar to that existing at the present day ? 



Although, owing to the lapse of time since the Chalk was 

 deposited, specific resemblance may be impossible, yet should generic 

 identity and more especially a marked similarity in the grouping of 

 the forms be admitted, then such facts must become of the greatest 

 interest. To determine what the prevalent fauna of the period was, 

 it is necessary to seek areas which are generally allowed to have been 

 free from the influences which led to the formation of the true Chalk 

 deposits. Such areas are situated in southern and south-western 

 Germany, comprising the Cretaceous deposits of Bohemia, Saxony, 

 the Hartz, and Westphalia. Here existed a molluscan fauna 

 resembling in all its main features that fauna of the present day which 

 occurs in decidedly subtropical regions. 



Although most of our leading text-books represent the appear- 

 ance of many Gastropoda — especially of such carnivorous forms as 

 Valuta and Fasciolavia, in the Maestricht Chalk and Faxe Limestones — 

 as novel and startling, and peculiarly foreshadowing the advent of the 

 Tertiary period, yet these genera seem to have existed throughout all 

 Upper Cretaceous time, on the borders of the South German con- 

 tinental area. Valuta, Conns, Stvombus, Tnyritella, Trochus, a.nd Fusus, as 

 also Cerithinm, Naiica, and Biiccimim, are by no means uncommon in 

 the strata of Bohemia and Saxony, and had a very wide extension 

 during the period which corresponds to that of our Upper Chalk. 

 Nor are these the only localities where such an assemblage has been met 

 with. In New Jersey, Clark and Williams have shown the presence 



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