This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ... as a relict, in spite of having witnessed the remarkable mutations from a semi-tropical to a semi-Arctic climate. Zonites is another characteristic snail of the Alpine region, extending south-eastward, like Pomatias, and thus indicating the possible direction from which the genus originally invaded the area. The genus ...
Read More
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ... as a relict, in spite of having witnessed the remarkable mutations from a semi-tropical to a semi-Arctic climate. Zonites is another characteristic snail of the Alpine region, extending south-eastward, like Pomatias, and thus indicating the possible direction from which the genus originally invaded the area. The genus Clausilia, which I have referred to on several previous occasions, and of which four species have been recorded from England, is well represented in the Alps. I have pointed out that from the general range of the Clausilias in Europe, both fossil and recent, we can infer that the genus originated somewhere in the south-east, or at least that the active centre of distribution during later Tertiary times was in that region. We find in the Alps a confirmation of the correctness of this view. In Miocene times the Alpine island as stated above, became joined to South-eastern Europe. This connection enabled the south-eastern fauna to invade the new peninsula which had thus been produced. Clausilias ought, therefore, to occur in abundance in the Alps, as they had henceforth free access to the peninsula from their headquarters. And that is the case. Even in the Western Alps in Switzerland, we still find eighteen species, whereas only three or four species cross the Pyrenees, the greater part of Spain being inhabited by only a single one. The latter (Clausilia bidentata) seems to be a much more ancient form than most other Continental species, for it enjoys a wide range in Western and Northern Europe, and occurs as far east as Austria, yet does not penetrate to the Alps. It appears as if its dispersal had originated in the west at a time when the Alpine area was still surrounded by the sea. It will be remembered that the pearl mussel (Margaritana marg...
Read Less