Proceedings of the Boston Society of Natural History (Volume 17)

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. 1861 Excerpt: ...of differentiation and gradual improvement by natural selection, has produced all the diversities of animals, in geological and present times. He did not think it fair to compare the present fauna of the world with the fauna of any geological horizon as known in one locality; and he thought this method of comparison had led to this idea of gradual development. Animal representatives were as numerous and diversified in early geological periods as now; he instanced the brachiopods. In the lowest beds of the Potsdam sandstone we find Lingula prima, and allied species are found in the Silurian, Devonian, Carboniferous, Permian, and Triassic, and with occasional interruptions up to the living species; there is an unbroken succession of Ungulc e up to the Jurassic strata; they are not found in the oolite, in the seven beds above the lias; in the lowest cretacean (neocomian) they appear again, then there is an interruption until the Tertiary epoch. About forty species of fossil Ungulce are found in these beds; only seven species of living lingulce were known to exist until he had recently added an eighth (L. Ravenelli, Ag.) from South Carolina, the first found on the American side of the Atlantic basin; when the shell gapes, one valve moves over the other, a circumstance rare in the brachiopods. He thought the persistence of this form through so extensive a period, the last no more perfect than the first, was a fatal objection to the theory of gradual development. Prof. Rogers admitted that the persistency of lingula, and other similar cases that might be adduced, were formidable objections to this theory; but he thought that Darwin would meet such objections by the fact that the vital characters of some animals fit them for resisting change and extinction better ...