304 



in the mud in places where no Hving ones could be found, 

 and they likewise occur in great quantities in certain old Indian 

 shell-heaps on many of the islands in Casco-Bay, upon the 

 coasts of which they do not now live. «That at a more remote 

 period», says Verrill, «the marine climate of this region was 

 still warmer, and the southern species were more abundant than 

 during the period when the Indian shell-heaps were formed, is 

 shown by the occurrence of great beds of oyster-shells a few 

 feet beneath the mud in Portland harbour, where they are as- 

 sociated with quahogs and several other southern species, 

 among which are Callista convexa, Turbonilla intemipta, and 

 Fecten irradians. The last is not known to live at present 

 north of Cape Ann, on the New-England coast» ; Callista con- 

 vexa occurs sparingly in shallow sheltered localities in Casco 

 Bay; «but the oysters (Ostrea virginiana) and «scallops» {Pecten 

 irradians) had apparently become extinct in the vicinity of 

 Portland harbour before the period of the Indian shell-heaps, 

 for neither of these species occurs in the heaps on the adjacent 

 islands, while the quahogs lingered on until that time, but 

 have subsequently died out everywhere in this region, except 

 at Quahog-Bay». Prof. Verrill says that he can explain the 

 presence of the southern species in no other way than by 

 supposing «that they are survivors from a time when the marine 

 climate of the whole coast, from Cape Cod to Nova-Scotia and 

 the Bay of Fundy, was warmer than at present, and these 

 species had a continous range from Southern New-England to 

 the Gulf of St. Laurence» M. 



This genial period is probably contemporary with that time 

 when Anomia and Zirphaea lived at West-Greenland. We have 

 perhaps also in certain places of West-Greenland a parallel to 



A. E. Verrill: Results of recent Dredging Expeditions on the Coast of 

 New-England. No. 5. The American Journal of Science and Arts, Third 

 Series, Vol. VII, 1874, p. 134— 138. Here cited after J. Geikie: Pre- 

 historic Europe, 1881, p. 502—03. 



