436 Mr. 11. M'Andrcw on the Distribution of Mollusca. 



Puncturella, Lepeta, Pilidium, and particularly by a remarkable 

 development of certain forms, such as Bela, Trophon, Neptuncttj 

 Maryarila, Astarte, Leila, and Crenella. The intermediate or, 

 as it lias been termed, " Celtic " province also ofifers the most 

 suitable dwelling-place to certain species and genera, most of 

 which extend their range, in diminished numbers, into one or 

 both of the adjacent regions. 



Assuming, then, that the fact of the existence of more than 

 one fauna or zoological province within the area referred to 

 (say, north of lat. 32'^) is established, it remains to define the 

 limits of each ; and this can only be done after careful observa- 

 tion. My own opinion is that the whole area may with pro- 

 priety be divided into five provinces, sufficiently characterized by 

 the species and genera predominating in each: viz., 1. Arctic; 

 2. Subarctic or boreal, extending from the Arctic circle to about 

 lat. 55° ; 3. Celtic (for which probably a more appropriate name 

 could be found), reaching its southern limit at a point yet to be 

 ascertained in the Bay of Biscay ; 4. Cantabrian or Lusitanian, 

 including the north coasts of Spain and west coast of Portugal ; 

 5. The Mediterranean, including the coast of Spain and Portugal 

 as far as Cape St. Vincent and the Atlantic shores of Morocco. 

 For the facts of distribution which have induced me to propose 

 this division, I refer to a report published in the Transactions 

 of the British Association for 1856. It will be seen that these 

 five provinces agree very nearly in their boundaries with those 

 represented by Prof. E.Forbes in his map of" Homoiozoic Belts," 

 published in Keith Johnston's ' Physical Atlas.' The claims of 

 the '^ Mediterranean province " to be considered distinct are 

 strongly maintained by Milne-Edwards. 



It must be explained that the foregoing observations do not 

 apply to the west shores of the Atlantic, which, with the excep- 

 tion of the Arctic and sub- Arctic species, present a fauna totally 

 unlike that of Europe and Africa. The fauna of the Azores, 

 which from its position might be expected to be found inter- 

 mediate between that of Europe and America, appears, as regards 

 Mollusca, to have no relation with that of the latter continent, 

 but to be in its general character Lusitanian, with the exception 

 of the littoral species, several of which arc common to the Ma- 

 deiran and Canary Islands and to tropical Africa. This fact is 

 particularly deserving of attention, from its apparent relation to 

 an ancient distribution of land different from the present, more 

 particularly as the currents which now prevail across the North 

 Atlantic from west to east, and from the Straits of Gibraltar 

 southward along the African coast, would seem to be opposed to 

 it. As regards the land and freshwater Mollusca of Europe 

 and North Africa, they appear to admit pf being divided into 



