54 



ARCTIC PROVINCE. 



laevigata and Mactra ponderosa. These are either 

 species described for the first time, or old ones 

 common to both sides of the Atlantic. Thus 

 Trophon harpularium, Gancellaria viridula, Natica 

 clausa (and probably also N. aperta), Margarita 

 cinerea, Pecten groenlandicum, Modiolaria laevigata, 

 and Mactra ponderosa, not only range to the strictly 

 Arctic shores of America, but most of them descend 

 as far on the western side of the N. Atlantic, as the 

 banks of Newfoundland, and the neighbourhood 

 of Cape Cod. This is the case, also, with Scalaria 

 groenlandica, and with Terebratula septigera and As- 

 tarte corrugata, two bivalves recorded from Finmark 

 only, in the northern fauna, but known under very 

 exceptionable circumstances farther to the south. 

 It is a striking and important fact, that several of 

 these species — so widely diffused on the American 

 coast, whilst, on the European they are restricted 

 to the Arctic circle — ranged, at the epoch of the 

 drift, as far south as the middle of England, and 

 the south of Ireland ; their fossil remains, undis- 

 tinguishable from recent specimens, are found in 

 the strata of the drift epoch in numerous British 

 localities at the present day. This fact cannot be 

 too strongly impressed on geologists, many of whom 

 have an impression that there is no marked dif- 

 ference between the fauna of the drift, and that 

 of the British seas at present, because the species 

 of shells found in the former are species still living. 

 But the presence of three or four such species — to 



