PURPURA. 283 



quently a succession of tubercular rows, forming internal 

 varices. None of the specimens which I have seen 

 from Canada and the United States are as large as ours ; 

 and I am consequently disposed to take a view opposite 

 to that which Forbes suggested, viz. that this species is 

 of American origin, and was introduced to the European 

 shores during the glacial epoch. The common character 

 of the fossils of that period in both continents shows 

 that a close connexion bv continuitv then existed 

 throughout the circumpolar area; and there is no evi- 

 dence that any migration took place from one continent 

 to the other. We must go back to the antecedent epoch 

 in order to trace the origin of this species ; and we there 

 find that it occurs for the first time in the Red Crag of 

 Suffolk. It is remarkable how the numerous varieties 

 figured by Mr. Searles Wood from that formation cor- 

 respond with those of the adjacent coast. 



The present species was named by Lister Purpura; 

 anglicance, or " white couvins ; " it is the Buccinum 

 Cornubiense bf Petiver, " le sadot " of Adanson, " the 

 purple-markiig whelke " of Borlase, B. purpuro-bucci- 

 num of Da Costa, B. anglicum of Gmelin, and B. angli- 

 canum of Lamarck ; the vulgar name in Ireland, accord- 

 ing to Smith and Rutty, is "horse winkles:" the fry 

 is probably B. breve and B. lave of Adams's papers in 

 the ' Linnean Transactions/ The P. lapillus of Risso 

 is Buccinum hamastoma of Linne. This latter species 

 inhabits the North Atlantic, from Brest southwards to 

 the Azores (including the coast of Senegal), as well as 

 the Mediterranean and Archipelago ; Morch gives the 

 Brazils as a locality, in the sale catalogue of the Count de 

 Yoldi's collection of shells. Between forty and fifty 

 years ago Mr. Charles Macculloch picked up three speci- 

 mens of this shell near St. Peter's Port, Guernsey, at 



