Of the Vicinity of Montreal. 423 



At Montreal, then, we have a littoral group of shells, a group 

 belonging to the Laminarian and Coralline zones, and a group 

 probably belonging to the Coralline and deep sea Coralline zones. 

 Perhaps the reason why the two shells characteristic of these last 

 zones have not yet been recognised as recent, is that the deep Sea 

 muddy bottoms on the American coast, have not yet been well 

 explored. It must be observed, however, that as the land was 

 rising at the time when these beds were deposited, in the lower 

 levels these three belts are stratigraphically superimposed on each 

 other, and mark not only difference of depth but lapse of time. 

 To what extent the precise order of these deposits, as observed at 

 Montreal, may hold in other parts of the St. Lawrence valley is 



* not yet known, but I hope to extend my observations with rela- 

 tion to this point ; and from facts published by other observers, I 

 have reason to believe that they will be found somewhat generally 

 prevalent. 



With respect to the divisions into which these deposits may be 

 sepa,rable, the presence of recent shells alone in the upper beds 

 would refer them to the Post-Pliocene period, while on similar 

 grounds the Leda clay and boulder clay might be regarded as 

 Newer Pliocene. Strictly speaking, however, the whole formation 

 belongs to the period of transition from the Pliocene to the mod- 

 ern epochs. The great boulder clay indicates a subsidence 

 at the close of the former, and the overlying beds the conditions 

 of deposit and of life during the re-emergence of the land ; so 

 that if we regard physical change as our guide, I should with 

 several previous writers on the subject, consider the whole of the 

 stratified beds overlying the boulder clay as one group of "modi- 

 fied " as distinguished from " unmodified " drift, a division which 

 I long ago adopted for the non fossiliferous drift of Nova Scotia, 

 This view vrould be farther strengthened by the piobability that 

 the high beaches containing recent shells may be contemporary 

 with the low lying clays having species supposed to be extinct, and 

 the farther probability that these last may yet be found living. 



. In the meantime, therefore, I prefer to consider these deposits as 

 extending through portions of the Newer Pliocene and Post Plio- 

 cene periods, without establishing any lines of division other than 

 those stamped on the deposits in the locality to which this paper 

 principally relates. 



By the kindness of Arthur Ross, Esq. of Montreal, I have been 

 favoured with a collection of fossil shells, from St. Nicholas, 15 



