My dear Sir

I trust that you received my letter some months since telling you that I had received your collection safe: it has been of the greatest possible use to me & my monograph would have been very imperfect without it: I thank you most sincerely for its use. I have been at work ever since I wrote last on fossil pedunculate cirripedia, (but my health makes my work very slow) & I have now fully described 33 species taking a typical valve in each genus. Several of your specimens are now in the hands of M^r Sowerby being drawn: this will take some time, but when finished every specimen shall be returned to you. I do not know whether you have attended much to the recent cirripedia, but I think you must from the sagacity & discrimination you have shown over the worn fossils; I have been able to add hardly anything to the accuracy of your drawings. The Palæontograph. Soc. has offered to publish my fossil species, so I shall go to press with them soon, & before the rest of my monograph: of course I will send you a copy.

I will now make a few remarks on the specimens sent me. (1) Anatifera cretae has interested me much; I have described a small cirripede clustered on an Antipathes from Madeira as a new genus under the name of Oxunaspis;¹ this I did unwillingly & only becaus it spoilt every other genus; your specimen will come nicely into this genus, which I consider intermediate between Scalpellum & Anatifera or Lepas.—² (2^d) Several facts make me believe, that as you suggest Pollicipes (or rather as I suspect Scalpellum) planulatus & Nilssonii are the same, & I have described them under one name, viz planulatum.—³ (3^d) P. rigidus is not the P. rigidus, of Sowerby of the Gualt but is its representative in the chalk; I have called it, P. elegans.—⁴ (4^th) Pollicipes maximus of Sowerby is certainly a Scalpellum ⁵ & has for synonyms, P. sulcatum of Sowerby; & your P. medius & solidulus:⁶ you will perhaps be surprised at this, as I was myself; but I have had a great series of specimens, & the variation in this species is extremely great.— (5^th) Your P. lævis, (that is judging from the valve lat infer. & valv lat sup.) is not the lævis of Sowerby;⁷ I have called it P. elongatus of you in Kroyer. 1B.—⁸ (6^th). P. dorsatus ⁹ is certainly distinct from P. elegans of Beck M.S.¹⁰ (NB I never intend to refer in print to M.S. names) (7^th) P. validus very distinct, but comes nearest to P. gracilis of Roemer.¹¹

Prof. Forchammer seemed to think that perhaps you could give me some duplicate specimens; I sh^d be very grateful for any, which when my monographs are completed will all go to British Museum; & this will tend to make your names known.— I sh^d feel particularly grateful, if you would take the trouble to answer me the following questions pretty soon.— (1) Skania age of beds? Von Buch states that only Upper Chalk occurs in north.¹² (2) Is White Chalk of Denmark same age or stage with Faxoe.¹³ (3) Do you know what the age of the Kreidemergel Grunsand (?) of Saliberg Quedlingburg is? I suppose it is in Westphalia.—¹⁴ (4) Is Legina Thy in Denmark?¹⁵ Do you feel pretty sure that the large valv. lat. sup. (named P. lævis & figured 9. Pl. V.) belongs to a loose valve marked P. lævis in softer white chalk in same little box with Anatifera cretæ.— 5^th & lastly, Do you feel pretty sure, & may I state so, that your Anatifera cretæ had only five valves?—¹⁶ I fear that I can hardly hope that you will take so much trouble as to send me the northern Anatiferae with your remark on their Range.— I have consulted Spengler, & think their can be no doubt regarding the Pedunculated cirripedes named by him;¹⁷ but if you could send me any of his sessile named species, it would be of vast service to me; or if you w^d. hereafter permit me, I would send some of the commoner forms for you to compare for me.—

Once again let me assure you how grateful I feel for the very great assistance which you have rendered me, & which shall be publickly acknowledged: I beg that you will give my thanks to Prof. Forchhammer, & believe me, dear Sir, with much respect. Yours faithfully & sincerely obliged | C. Darwin

P.S. There is a specimen marked “Svenstrup Nolle Grunsand”—is this in Skania, & what age is the bed?? Is it near Kopinge?