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Updated: May 17, 2025
If the different islands have their representatives of Geospiza, it may help to explain the singularly large number of the species of this sub-group in this one small archipelago, and as a probable consequence of their numbers, the perfectly graduated series in the size of their beaks. In land-shells this law of distribution does not appear to hold good. In my very small collection of insects, Mr.
St. Helena, situated so remote from any continent, in the midst of a great ocean, and possessing a unique Flora, excites our curiosity. The eight land-shells, though now extinct, and one living Succinea, are peculiar species found nowhere else. Mr. Cuming, however, informs me that an English Helix is common here, its eggs no doubt having been imported in some of the many introduced plants. Mr.
Gould has conclusively shown that many land-shells have thus been distributed over the Pacific by man's agency. These cases of introduction are most plaguing. Have you not found it so in the Malay Archipelago? It has seemed to me, in the lists of mammals of Timor and other islands, that several in all probability have been naturalised.
Lucia; then turned westward between the latter island and Martinique; and that the mighty estuary formed for a great part at least of that line the original barrier which kept the land-shells of Venezuela apart from those of Guiana. A 'stretch of the imagination, doubtless: but no greater stretch than will be required by any explanation of the facts whatsoever. And so, thanking Mr.
To the species therein described are added certain new ones, announced by Pfeiffer since the publication of his work, and others, recorded for the first time in this volume. It will be seen that a great part of the Australian land-shells is as yet unfigured.
The main points of interest consist, first in some highly fossiliferous strata, belonging to the Devonian or Carboniferous period; secondly, in proofs of a late small rise of the land; and lastly, in a solitary and superficial patch of yellowish limestone or travertin, which contains numerous impressions of leaves of trees, together with land-shells, not now existing.
Moreover a fact which I certainly did not expect the western side of this supposed land, namely, Trinidad, Tobago, Grenada, the Grenadines, St. Vincent, and St. Lucia, have, as far as land-shells are concerned, a Venezuelan fauna; while the eastern side of it, namely, Barbadoes, Martinique, Dominica, Guadaloupe, Antigua, etc., have, most strangely, the fauna of Guiana.
We see the same fact in geographical distribution; for instance, in the land-shells and coleopterous insects of Madeira having come to differ considerably from their nearest allies on the continent of Europe, whereas the marine shells and birds have remained unaltered.
We see the same fact in geographical distribution; for instance, in the land-shells and coleopterous insects of Madeira having come to differ considerably from their nearest allies on the continent of Europe, whereas the marine shells and birds have remained unaltered.
Acheul, in the suburbs of Amiens, where the old alluvium lies at an elevation of about 100 feet above the level of the river Somme. At both levels fluviatile and land-shells are met with in the loam as well as in the gravel, but there are no marine shells associated, except at Abbeville, in the lowest part of the gravel, near the sea, and a few feet only above the present high-water mark.
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