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"No, my boy, but I'd gladly have sacrificed a finger for such a find!" "What find?" "This shell," I said, displaying the subject of my triumph. "But that's simply an olive shell of the 'tent olive' species, genus Oliva, order Pectinibranchia, class Gastropoda, branch Mollusca " "Yes, yes, Conseil! But instead of coiling from right to left, this olive shell rolls from left to right!"
This invasion of the land was prefaced by a previous invasion of the Cretaceous sea by modern forms of mollusca and fish. It is easy to imagine how an analogous change might come about in the existing world. There is, at present, a great difference between the fauna of the Polynesian Islands and that of the west coast of America.
It would, indeed, have been a great anomaly if there had been a true passage between a deposit contemporaneous with existing species of mollusca, and one in which all the mollusca appear to be extinct.
Modifications, unserviceable. Moggridge, J.T., on habits of spiders; on habits of ants. Moles, numerical proportion of the sexes in; battles of male. Mollienesia petenensis, sexual difference in. Mollusca, beautiful colours and shapes of; absence of secondary sexual characters in the. Molluscoida. Monacanthus scopas and M. Peronii. Monboddo, Lord, on music.
It is nowhere many miles wide; but this narrow point of land has hitherto proved a barrier to the migration of many species of mollusca.
He informed me that the fossil fauna of this Scotch glacial deposit exhibits not only the species but also the peculiar varieties of mollusca now characteristic of very high latitudes. Their large size implies that they formerly enjoyed a colder, or, what was to them a more genial climate, than that now prevailing in the latitude where the fossils occur.
It is clear that the more ancient the existing mollusca, or the farther back into the past we can trace the remains of shells still living, the more easy it becomes to reconcile with the doctrine of transmutation the distinctness in character of the majority of living species.
In distinguishing the latter from formations accumulated in the sea, we are chiefly guided by the forms of the mollusca. In a fresh-water deposit, the number of individual shells is often as great as in a marine stratum, if not greater; but there is a smaller variety of species and genera.
One-eighth natural size. a. Exterior. b. Some species of mollusca and other fossils range through the whole series, while others are confined to particular subdivisions, and Forbes laid down a law which has since been found of very general application in regard to estimating the chronological relations of consecutive strata.
He gave me some rare shells, for I at that time collected marine mollusca, but with no great zeal. My summer vacations during these two years were wholly given up to amusements, though I always had some book in hand, which I read with interest. During the summer of 1826 I took a long walking tour with two friends with knapsacks on our backs through North wales.
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