4 P. A. OYEN [No. 12 



Macoma calcaria Chemn. 

 Mya truncata L. 

 Saxicava pholadis L. 

 Zirphaea crispata L. 

 Siphonodentalium vitreum M. Sårs. 

 Antalls striolata Stimps. 

 Lunatia groenlandica Beck. 

 Balanus crenatus Brug. Darw. 



Even a glance at this list will assure us of the occur- 

 rence of fossil groups of different stratigraphical ages; and a 

 more critical study shall make this fact grow still more con- 

 vincing upon us. That, for instance, the Arca-Siphonodentalium- 

 group should be contemporaneous with the Mytilus-series does 

 not agree with our present knowledge of the distribution and 

 occurrence of those species. It would be much more reasonable 

 too that the two species of Area, viz. glacialis and pectun- 

 culoides, appeared in different layers rather than in quite the 

 same stratigraphical deposit. And, so on, we might pass through 

 the whole list making our critical and theoretical remarks. It 

 is, however, highly remarkable how well, this criticism coincides, 

 sometimes even to rather minute details, with the results of 

 stratigraphical investigations. In this way we are able to con- 

 struct the following line of geological evolution in this place: — 



Ground moraine. 

 Fluvio glacial deposits. 

 Portlandia sp. (? arctica). 

 Area glacialis. 

 Abra longicallis. 

 Portlandia lenticula. 

 Area pectunculoides. 

 Pecten septemradiatus. 

 Macoma baltica. 

 Mytilus edulis. 



