14 P. A. ØYEN. PORTLANDIA ARGTICA GRAY [No. 3. 1911] 



in the clay layers at Kolvik that this fauna did not perish by cata- 

 strophism when the ice melted away, and when the ice-front 

 retired. The process of melting was really rather slow and oscilla- 

 ting, and to some extent the animals wereable to accomodate them- 

 selves for the new condition of their surroundings. Only the most 

 sensitive ones were obliged to emigrate. The ground was left to 

 the survivors which, however, though adapting themselves to the 

 new surroundings, were in their turn to partly retire and give 

 place, more or less, to the immigrating inhabitants of the sea, 

 that made their appearance, when in the course of time, as well 

 climate as sea-water grew more favourable to animal life of 

 more temperate regions. 



Printed 8*b December 1911. 



