10 P. A. ØYEN [No. 3 



Balanus porcatus da Costa, Darw. 

 Balanus crenatus Brug., Darw. 

 Verruca stroemia Mull., Darw. 



IV. 



In this group we have to include a number of fossils ranging 

 through different periods, from the Pholas-niveau down to 

 our own time. In fact, we may be able to trace the invasion 

 of some of those forms as being characteristic for certain periods 

 or divisions, for instance, Cardium edule L. for the Pholas- 

 niveau 1 , Anomia striata Brogchi for the Mactra-niveau 2 , 

 Ostrea edulis L. for the Tapes-niveau 3 , and we may be 

 quite sure that a great part of the rare and temperate forms did 

 not invade the waters of our fiords or crowd the sea along the 

 Norwegian coast till the dry and hot climate set in that was 

 so characteristic of the period when the deposits of the Trivia- 

 niveau 4 were laid down. During the periods of the Os trea - 

 niveau and the Mya-niveau 5 , we find a number of survivors 

 from earlier periods hut only some few forms that did not before 

 now make their appearance, at least, in the shallow waters 

 along our shores. 



The following list gives the mollusca, and gastropoda, and 

 some other forms of this group, 



Crania anomala Mull. 



Terebratulina caput serpentis L. 



Anomia striata Brocchi. Length 46 mm. 



Ostrea edulis L. 



Pecten varius L. 



Pecten opercularis L. 



1 P. A. Øyen: Nye bidrag til bestemmelse af Pholas-ni v ea u et, 1907. 



2 P. A. Øyen: Det sydlige Norges boreale strandlinje, 1906. 



3 P. A. Øyen: Tapes decussatus Lin. og Ta pes -ni v eau e ts geologiske 

 stilling, 1905. 



4 P. A. Øyen: Trivia-ni veauet ved Svelvik 1908. 



5 P. A. Øyen: Kvartær-studier i den sydøstlige del af vort land, 1908. 



