Clypeus ploti Fossil

PRESCRIBED SOURCE

Clypeus Ploti Fossil

Description. 'A fossil, clypeus ploti, named after Robert Plot (1640-96), first Keeper of the Ashmolean Museum, whose portrait hangs over the fireplace. The fossil is described by Plot in The Natural History of Oxfordshire (Oxford, 1677), pp. 90-1 and Table II, figs. 5 & 6; and by his successor Edward Lhuyd (1660-1709) in Lithophylacii Britannici Ichnographia (London, 1699), p. 48 and Table 13, catalogue no. 971. The original type-specimen, whose present whereabouts are unknown, was found at Fulbrook, near Burford. Diameter: 82mm.' 

Source. Museum of the History of Science, University of Oxford, ID no. MHS 36880. The text above originates in a former display label. Current location: 'The Ashmolean Museum' display case, Top Gallery, Museum of the History of Science, along with the elephant's tooth. 

The relevant text from Plot's Natural History of Oxfordshire is as follows: 

30. Of Brontiae therefore, or Ombriae (call them which you will) we have several sorts in Oxford-shire, which yet all agree in this, that they are a sort of solid irregular Hemisphears; some of them oblong, and having somwhat of an oval; others either more elevated, or depressed on their bases. All of them divided into five parts, most times inequal, rarely equal, by five rays issuant from an umbilicus or center, descending from it down the sides of the body, and terminating again somwhere in the base. They are never found in beds together, like some other formed stones, nor that I have yet heard of (says the Ingenious Mr. Ray) in great numbers in one place: but in the latter I must take leave to inform him, that though I think it in the main to be true, yet that at Tangley, Fulbrook, and all about Burford, they are found in such plenty, that I believe it were easie in a little time, to pro∣cure a Cart-load of the first sort of them, carefully exhibited in Tab. 2. Fig. 9, 10.

31. Whose innermost texture, though it seem to be nothing [page 91] more than a course rubble-stone, yet is thinly cased over with a fine laminated substance (the plates lying obliquely) much like Lapis Judaicus: In form they are flat, depressed upon the basis; in colour generally yellow, their rays made of a double rank of transverse lines, with void spaces between the ranks, visible enough on the top of the stone Fig. 9. but not so distinguishable on the bottom Fig. 10. the whole body of the stone, as well as the spaces included within the rays, being elsewhere filled with Annulets, much more curiously wrought by Nature, than by the tool of the Graver.

32. The center of these rays, by Pliny called Modiolus, by Aristotle, Ʋmbilicus, is never placed on the top of the stone, but always inclining to one side, as that at the bottom do's to the other; the Axis lying obliquely to the Horizon of the stone. Which gave occasion to a Learned Society of Virtuosi, that during the late Usurpation lived obscurely at Tangley, and had then time to think of so mean a subject, by consent to term it the Polar-stone, having ingeniously found out, by clapping two of them together, as suppose the Fig. 9, and 10. that they made up a  Globe, with Meridians descending to the Horizon, and the Pole elevated, very nearly corresponding to the real elevation of the Pole of the place where the stones are found.

 
Credit: Howard Hotson (May 2018) 

Further reading. David A Berry, Dodos and Dark Lanterns: Highlights of Ashmolean History (Oxford 2013), pp. 24-29.