No. 5.] NATURAL HISTORY SOCIETY. 281 



Various modern indications point to the same conclusions. 

 Verrill has described little colonies of southern species still sur- 

 viving on the coast of Maine. There are also dead shells of 

 these species in mud banks, in places where they are now extinct. 

 He also states that the remains in shell-heaps left by the Indians 

 indicate that even within the period of their occupancy some of 

 these species existed in places where they are not now fou id. 

 Willis has catalogued some of these species from the deep b lys 

 and inlets on the Atlantic coast of Nova Scotia, and has showa 

 that some of them still exist on the Sable Island banks * 



Whiteaves finds in the Bradelle and Orphan bank littor il 

 species remote from the present shores, and indicating a tiini 

 when these banks were islands, w^hich have been submerged by 

 subsidence, aided no doubt by the action of the waves. 



It would thus appear tliat the colonisation of the Acadian 

 Bay with southern forms belongs to the modern period, but tha'i 

 it has already passed its culmination, and the recent subsidence 

 of the coast has no doubt limited the range of these animals, and 

 is probably still favouring the gradual inroads of the Arctic 

 fauna from the north, w^iich, should this subsidence go on, will 

 creep slowly back to reoccupy the ground which it once held ia 

 the Post-pliocene time. 



Snch peculiarities of distribution serve to show the effects of 

 even comparatively small changes of level upon climate, and 

 upon the distribution of life, and to confirm the same lesson of 

 caution in our interpretation of local diversities of fossils, which 

 geologists have been lately learning from the distribution of cold 

 and warm currents in the Atlantic. Another lesson which they 

 teach is the wonderful fixity of species. Continents rise and 

 sink, climates change, islands are devoured by the sea or restored 

 again from its depths ; marine animals are locally exterminated 

 and are enabled in the course of long ages to regain their lost 

 abodes; yet they remain ever the same, and even in their varie- 

 tal forms perfectly resemble those remote ancestors which are 

 separated from them by a vast lapse of ages and by many physi- 

 cal revolutions. This truth which I have already deduced from 

 the Post-pliocene fauna of the St. Lawrence Valley, is equally 

 taught by the molluscs of the Acadian Bay, and by their Arctic 

 relatives returninu; after lonu' absence to claim their old homes. 



* 

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* Acadian Geology, p. 37. 



