SUMMARY. W 



I have already directed attention to the fact that when the 

 European and more distinctly ' Mediterranean'' forms have 

 been removed, and the catalogue has been cleared of everything 

 but what we may be permitted to call its ' Atlantic element,' 

 the actual species which range beyond the limits of a single 

 archipelago are marvellously few, — about 4 or 5 being common 

 to the Madeiras and Azores, about 5 or 6 to the Madeiras and 

 Canaries, and about 1 to the Canaries and Cape Verdes ; whilst 

 between the Azores and Canaries there are only about 5, and 

 between the Madeiras and Cape Verdes about 1. Moreover 

 there are strong reasons for suspecting that some even of these 

 (perhaps indeed most of them) may have been accidentally 

 transported amongst the islands, through indirect human agen- 

 cies, at a comparatively recent date ; so that we are driven to 

 conclude that, so far as the absolute species are concerned, of 

 which their aboriginal faunas are respectively made up, the 

 Groups are practically almost independent of each other. And 

 yet, in spite of this, I have had occasion to insist more than 

 once upon the many characteristic types which, under the 

 aspect of totally different but nevertheless allied species, per- 

 meate to a greater or less extent the entire t province,' — giving 

 to it an amount of unity, through its several component parts, 

 which it is scarcely possible not to recognize. As they have 

 already been enumerated in detail, I need not recapitulate them ; 

 but we may just call to mind how that the Janulus section of 

 Patula crops up at the Madeiras and Canaries, but has no ra- 

 presentative at the Azores and Cape Verdes, — how the Helici- 

 deous department Leptaxis is dominant in the Azores, Madeiras, 

 and Cape Verdes, and yet does not exist at the Canaries, — how 

 the Discula group, which attains its maximum in the Madeiras, 

 extends feebly to the Canaries but is absent from the Azores and 

 Cape Verdes, — how the curious genus Graspedopoma puts in an 

 appearance in the three northern archipelagos, but has no 

 exponent in the southern one, — how the Azores and Canaries 

 harbour the minute Hydroccena, which nevertheless does not 

 occur at the Madeiras, — and how an essentially 'Atlantic' type 

 of Pupa is scattered broadcast over the whole region. Such 

 facts as these, and many others of a like nature, betoken an 

 individuality of the district which cannot well be ignored, even 

 whilst the actual species (of a truly Atlantic character) which 

 wander beyond the limits of a single cluster are so few in 

 number as to be well-nigh inappreciable. The latter circum- 

 stance, however, is quite in harmony with the perfectly mar- 

 vellous segregation which is so conspicuous in most of the 

 archipelagos, particularly in the Madeiran and Canarian ones, — 

 an overwhelming proportion of the species being confined to 



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