My Dear Sir

On the other leaf I have copied your list and stated what I believe will be found correct relative to each genus. My conclusion would be that the fossil shells of Navedad have not a particularly tropical character. The Cassis is small—a larger species is found in the Medⁿ. though the large sorts are tropical. It may be doubted if Sigaretus be really found in the Medⁿ. it is probable that it may belong to S. Australia. Perna abounds in tropical latitudes—and if any are found on the S. Australian coast—they are scarcely known—fossil species are found in Piedmont & Normandy &c. Harpa is one of the most decidedly tropical genera. Conus, Cypræa, Ovulum, Mitra, Terebra—Meleagrina, Perna, Voluta—Fusus—Triton &c may be regarded for the most part as tropical—though there are perhaps some exceptions in each genus. There is scarcely a genus of any extent that has not some species in temperate and extra-tropical zones. Thus there are Cones, Cowries, Mitres, Fusi, Tritons &c in the Medⁿ:

Concerning Trigonocelia I believe there is not known any recent species: fossil species exist in our Europæan tertiary beds. How can D’Orbigny admit Trigonocelia if he turn out Cucullæa? Crassatella is not peculiarly characteristic of the Australian seas, some species are found in the Atlantic and Indian seas.

You know the recent Struthiolariæ belong to N. Zealand—and the Trigonia abounds at or near to Sydney, N. S. Wales: the genus is found fossil almost everywhere—

Thus have I, to the best of my abilities answered your queries—¹ I hope satisfactorily and remain | My Dear Sir Your very obliged | G B Sowerby 7^th Feb^y. 1846—

Charles Darwin Esq^r. Gastridium. I know no recent species; other fossil species are found “aux environs de Paris”. Monoceros, the greater number belong to the Southern parts of S. America— Voluta, ranges as you say to “Str. of Magellan” there are also some fine South Australian species (magnifica, fluctuata, Turneri, Zebra, pulchra &c) though I believe the greater number and those with most brilliant colours are tropical. Oliva—abounds in tropical latitudes; though some fine species are found to the northward: it can scarcely be regarded as in any degree characteristic of other than the tropics. Pleurotoma—few species belong to temperate or Mediterⁿ. zones. Fusus—ranges to high northern latitudes, though I believe the finer species are intertropical. Turritella Trochus Your Navedad species might belong to temperate latitudes as far as they are concerned. Cassis—in general tropical, some few small species are found north of the tropics—there are also some S. Australian species. Pyrula—tropical Triton—some large species are found in M: Medⁿ: & S. Australian. Sigaretus—not entirely confined to tropical climates Natica—has a most extensive range. Bulla—also. Terebra—though not entirely confined to tropical latitudes, is nevertheless very characteristic of them. Dentalium—very nearly as Natica, though the large & fine species belong to the tropics. Corbis—I believe tropical—as there is some uncertainty about your Navedad species, it would not be right to draw any conclusion from it. Cardium—has a very extensive range. Venus—d^o. Pectunculus—d^o. its greatest developement in the Medⁿ. Cytherea—has a very extensive range. Mactra—d^o. Pecten—d^o.