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Darwin Correspondence Project

From G. B. Sowerby   17 January 1846

My Dear Sir

You will probably have expected this sooner, the points to be settled were however difficult— After the most careful examination of all the specimens the result will appear in the separation of two sorts from T. ambulacrum this I have done, not because I am myself fully satisfied of its propriety, but because I found characters which would be considered satisfactory (as distinguishing characters) by some (D’Orbigny inter alia) characters which some would regard as specific, others as only variations—however my opinion is that wherever a combination of characters distinguishing one subject from another exist, they should always be noticed, whether they be considered as the characters of a species or only of a variety.1

I will now explain my operations 1st. those of Huafo & Mocha I have described as T. Chilensis 2d that of Port Desire, together with the Navedad (T. carinifera) and several specimens without locality, but numbd. 632 I have described as T. Patagonica. 3d the St. Julian must be regarded as neither more nor less than T. ambulacrum 4th I wd. strike out from the Navedad series the one resembling T. carinifera 5th Also the T. Ambulacrum with somewhat variable external characters from the Port desire list. 6th Of the additional specimens one (numbered 632) is already disposed of; the two others are such mere casts or fragments that they cannot be brought into the account. 7th I must now add with respect to the fragments from Navedad formerly said to resemble carinifera, but which I now recommend you to strike out, that, one fragment also belongs to T. Patagonica, the rest are probably Ambulacrum, but are very indistinct.

The specimens shall be packed up on Monday or Tuesday and sent to the Geol: Society for you—

I am My Dear Sir | Your very obliged | G B Sowerby 17th Jany /46—

N.B. Too late for post.


Refers to shells brought to Sowerby by CD in November 1845. See CD’s letter to G. B. Sowerby, 12 [November 1845], and intervening letters. CD may have queried Sowerby’s species determinations, or the additional work on Turritella may indicate that the two specimens from Navidad, reported missing in CD’s letter of [1 December 1845], had been found. Sowerby had already been paid for his descriptions, see letter to G. B. Sowerby, [9? December 1845], n. 1. Two fragments of Navidad Turritellae are included among the descriptions Sowerby gives in the appendix to South America (pp. 256–7), but it is not known whether these are the missing specimens.


Describes his reasoning in classifying CD’s Turritella ambulacrum specimens into two sorts. GBS holds that distinguishing characters, whether of species or varieties, should always be noticed. [See South America, appendix, pl. III, fig. 49.]

Letter details

Letter no.
George Brettingham Sowerby
Charles Robert Darwin
Sent from
Source of text
DAR 43.1: 1c–2
Physical description
ALS 3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 943,” accessed on 28 September 2023,

Also published in The Correspondence of Charles Darwin, vol. 3