Fossil sepia, described 1829
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Extract from a geological map of Black Ven, Charmouth showing the location of the Upper, Middle and Lower Belemnite Marls so called due to the abundance of the fossilised remains of the cephalopod they contain. From W D Lang, "The geology of the Charmouth Cliffs, beach and fore-shore", Proceedings of the Geologists' Association, vol 25 (1914). GSL Library collections.
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Anterior sheath and ink bag of ‘Belemnosepia’ found by Mary Anning in 1828 and later imagined reconstruction of the creature from W Buckland, “Geology and mineralogy considered with reference to natural theology” (1836). GSL Library collections.
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The third Mary Anning related discovery in William Buckland’s 1829 paper was that of fossil sepia - that is fossilised ink sacs. Anning identified these as deriving from a belemnite, an extinct cephalopod whose closest modern relative are squids and cuttlefish. Belemnites lived during the Jurassic and Cretaceous periods (c.200-65.5 million years ago). The soft, squid like body decays and what is usually only left is the fossilised remains of the hard internal, bullet-shaped guard or rostrum.
Although Anning was quite sure of her identification, Buckland wasn't, so hedged his bets:
"An indurated black animal substance, like that in the ink-bag of the cuttle-fish, occurs in the lias at Lyme Regis...It is nearly of the colour and consistence of jet, and very fragile, with a bright splintery fracture; its powder is brown, like that of the painter's Sepia it occurs in single masses, nearly of the shape and size of a small gall-bladder....The author infers, that the animal from which these fossil ink-bags are derived, was some unknown cephalopode, nearly allied in its internal structure to the inhabitant of the belemnite the circular form of the septa showing that they cannot be referred to the molluscous inhabitant of any nautilus or Cornu-ammonis." From W Buckland, "On the discovery of a new species of Pterodactyle; and also of Faeces of the Ichthyosaurus; and of a black substance resembling Sepia in the Lias at Lyme Regis", Proceedings of the Geological Society of London, vol 1 (1829).
Anning's identification would later be confirmed by the Swiss naturalist Louis Agassiz (1807-1873) during his trip to Lyme Regis in 1834.
The fossilised, powdery ink could be reconstituted into a drawing medium (the image below is an example). Aptly, it is of a Jurassic animal - an ichthyosaur skull from the private fossil collection of Anning’s friend and fellow Lyme resident Elizabeth Philpot (1780-1857). Philpot had first sent a copy of her drawing to Buckland’s wife Mary née Morland (1797-1857) but seems to have been so pleased with the outcome that she made a number of copies.
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Study of the skull of an ichthyosaur made in fossil sepia, probably by Elizabeth Philpot, [1833-1834]. This drawing was given to the Society by Henry De la Beche in March 1834 but it is a very close copy of that sent to Mary Buckland by Philpot in December 1833. Archive ref: LDGSL/642.
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