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VI.—The Southern Character of the Molluscan Fauna of the Coralline Crag Tested by an Analysis of its more Abundant and Characteristic Species1

Published online by Cambridge University Press:  01 May 2009

F. W. Harmer
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Extract

The close resemblance between the Molluscan fauna of the Coralline Crag and that of the Mediterranean at the present day has long been known and is universally recognized. It has been customary, however, to take the whole list of shells from this deposit, for the purpose of comparison, without reference to the greater or less abundance of the different species; but in discussing the affinities of the fauna from this, or indeed from any other horizon of the East Anglian Crags, it may be misleading to attach as much importance to the presence of a shell, of which only one or at the most a very few specimens have been discovered during so many years, as to the occurrence of forms which are found in such countless profusion as sometimes to compose a large proportion of the whole number of the shells present. Out of about 440 species of Mollusca from the Coralline Crag given by Mr. Wood in his well-known Monograph (excluding varieties), nearly 90 are said to be represented by unique specimens only, while more than 100 others have very rarely been met with. It is true that some of these rarer forms may be only locally rare, although it is worthy of notice that, with few exceptions, the species which are common in the Diestien beds of Belgium, believed to be approximately contemporaneous with the Coralline Crag, are also common in that deposit. On the whole, without ignoring altogether the existence of the rarer forms, it seems that a consideration of the general facies of the fauna of each of the different horizons of the Crag, and of its characteristic fossils, is more important and is likely to give more reliable results than an analysis of all the species of each bed, irrespective of the greater or less frequency with which they have been found.

Type
Original Articles
Information
Geological Magazine , Volume 3 , Issue 1 , January 1896 , pp. 27 - 31
Copyright
Copyright © Cambridge University Press 1896

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Footnotes

1

Read before Section C of the British Association at Ipswich, Sept. 12th, 1895.

References

page 27 note 2 Palæontographical Society (1848, etc.).

page 27 note 3 Broeck, Van den, Introduction au Memoire de M. P. H. Nyst sur la Conchyliologie des Terrains tertiaires de la Belgique. Bruxelles (1882).Google Scholar

page 28 note 1 Étude préliminaire des coquilles fossiles des Faluns de la Touraine. Rennes: Paris (1886).Google Scholar

page 28 note 2 Ponzi and Meli, Mem. R. Accad. dei Lincei, ser. 4, vol. iii, p. 672 (1887).Google Scholar

page 28 note 3 Bell, A., Catalogue des Moll. Foss. des Marnes Blues de Biot, près Antibes: Journ. de Conch. Paris (1870).Google Scholar

page 28 note 4 Zaccari, , Catalogo dei Fossili del Monte Mario, Collezione Rigacci. Roma.Google Scholar

page 29 note 1 Professor Prestwich gives a list of about a dozen species of Mollusca which he claims as Northern (Q.J.G.S., vol. xxvii, 1871, p. 135). Five of these, however, range to the south as well as to the north of our shores; and as to the rest, with the exception of the one already named (Buccinopsis Dalei), and another, Trichotropis borealis, which is very rare in the Coralline Crag, he follows Dr. Gwyn Jeffreys in considering shells regarded as extinct by Searles Wood and others as varieties merely of existing species. For example, he believes Astarte Omalii to be the equivalent of A. undata, an American shell, and Tellina obliqua that of T. lata, an entirely distinct form. Mr. Wood had the opportunity of weighing Dr. Jeffreys' views, and he has given in the Supplement to his Monograph his reasons for differing from them. I agree with Mr. Clement Reid and others in following Mr. Wood's opinion as to this.

page 30 note 1 The figures now given are slightly different to those originally stated, but the conclusions to be drawn from them are not affected by the alteration.

page 30 note 2 Q.J.G.S., vol. xxvii, p. 134 (1871).Google Scholar

page 31 note 1 Mr. C. Reid mentions that in some of the Coral islands of the South Seas, boulders which reach the shore on drift-wood are the perquisite of the chiefs.