LI@PISTEHA: 257 
Volgian of Moscow, which were identified by Prof. Pavlow, but their resemblance 
to Rouillier’s figure is not quite so close. Some of the smaller specimens approach 
P. peregrina (VOrbigny'), which is said to differ from P. Orbigniana by smaller 
curvature of the ventral margin, the presence of a shallow depression extending to 
the ventral margin below the umbones, and by the ornamentation consisting of 
radial rows of minute tubercles instead of linear ribs. One specimen from Spilsby, 
however, shows both types of ornamentation, suggesting that the two species are 
not really distinct. The hinge is not seen in any of the Enelish specimens of P. 
Orbigniana, but the figure given by Rouillier, although not quite satisfactory, is 
suggestive of Panopea; the form of the shell, however, resembles that of some 
Jurassic species of Plewromya. 
Distribution.—Spilsby Sandstone (zone of Belemnites lateralis) of Donnington. 
Family—POROMY ACID As, Dall. 
Genus—LiopistHa, I’. B. Meek, 1864. 
(‘Check List Invert. Foss. N. America,’ pp. 12, 32; T. A. Conrad in Kerr’s ‘Report Geol. Survey 
N. Carolina,’ vol. i, 1875, Appendix A, p. 28; Meek, ‘Invert. Cret. and Tert. Foss. U. Missouri,’ 
1876, p. 227.) 
Section—Pstnomya, Meek, 1876. 
(Ibid., p. 229.) 
LiopistHa (PSILoMYA) GIGANTEA (Sowerby), 1818. Plate XLIII, figs. 3, 4; Plate 
XLIV, figs. 1, 2. 
1811. Corsuna?, J. Parkinson. Organic Remains, vol. ui, p. 226. 
1818. —- GIGANTEA, J. Sowerby. Min. Conch., vol. iii, p. 13, pl. ccix, 
figs. 5—7. 
1850. PHoLapomya — A. d’Orbigny. Prodr. de Pal., vol. u, p. 157. 
1854. Tueris — J. Morris. Cat. Brit. Foss., ed. 2, p. 227. 
1865. — ? — F. J. Pictet and G. Campiche. Terr. Crét. Ste. Croix 
(Matér. Pal. Suisse, ser. 4), pp. 199, 210. 
L870, oro F. Stoliczka. Paleeont. Indica, Cret. Fauna S. India, 
vol. ii, p. 42. 
1882. LroristHa — P. de Loriol. Gault de Cosne, p. 45, pl. vi, figs. 1—5. 
1 Murchison, Verneuil, and Keyserling, ‘Géol. de la Russie de Europe,’ vol. 11 (1845), p. 468, 
pl. xl, figs. 1O—12. The hinge is figured by Zittel, ‘Handbuch d. Paliont.,’ vol. ii, p. 125, fig. 179, 
and ‘ Grundziige d. Paliont.,’ ed. 2 (1903), p. 330, fig. 732. 
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