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Darwin Correspondence Project

From John Morris   1 March 1856

Kensington

Mar 1. 56

My dear Sir

The only evidence on the existence of living land Mollusc in England is the Helix labyrinthica Say, of the eocene Hordwell deposits & considered by Mr. Wood1 to be identical with the American species of Say.2

The identity of the Melaniopsis buccinoidea of the Woolwich (lower eocene) series is probably doubtful with the Nile form. although I believe considered so by Ferrussac & Deshayes.3 So that is but little evidence of many existing forms in the older tertiary period.

Nor is there much evidence respecting the greater duration of life of the fresh water-testaceæ to the marine gasteropoda none of the eocene species ranging into the upper strata

I can only call to mind at present the genus, Strophostoma or Ferrusina of the miocene which is an extinct genus—

The relation of the gasteropoda found in the Mammalian beds at Grays4 &c &c to the marine deposits, is not definitely settled—ie whether they are equivalent to or superior to some of the deposits of the glacial or pleistocene epoch

There is a notice (I think in the journal (geological)) of some deposits in which I believe it is mentioned that a stratum of extinct freshwater shells, cover a deposit of marine mollusca of still existing species. I believe it is alluded to to by Sir R. Murchison in his Alps paper, but I have not the reference.5 I will look for it & others and write you again—

The best evidence is (as you are aware) that the freshwater genera as genera have survived many mutations of the surface, and outlived many of the marine genera, of course I allude to the still living genera of Physa Planorbis, Melanopsis, Cyrena, Paludina, &c in the Purbeck & Wealden—so in the lower and middle tertiary, &c

Yours sincerely | John Morris C Darwin Esq

CD annotations

Top of first page: ‘On age of Land & F.W. & marine Mollusca.—’ pencil; ‘18’6 brown crayon, circled brown crayon

Footnotes

Searles Valentine Wood was an expert on the fossil Mollusca of the East Anglian Crag.
Thomas Say.
Férussac and Deshayes 1820–51.
Grays near Thurrock, Essex, the site of fluviatile deposits from the Crag period.
Morris refers to Murchison 1847, in which the order and implications of the fossiliferous strata of Œningen are discussed. Roderick Impey Murchison reconsidered his conclusions in Murchison 1849, pp. 233–7, having decided that the Alps had experienced geological upthrust so violent that some strata had been completely overturned.
The number of CD’s portfolio of notes on the means of geographical dispersal of plants and animals.

Summary

Informs CD on age of land, freshwater, and marine Mollusca.

Letter details

Letter no.
DCP-LETT-1835
From
John Morris
To
Charles Robert Darwin
Sent from
Kensington
Source of text
DAR 205.2: 246
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 1835,” accessed on 17 June 2019, http://www.darwinproject.ac.uk/DCP-LETT-1835

Also published in The Correspondence of Charles Darwin, vol. 6

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