THRACIA. 241] 
margin nearly straight, with a considerable ventral slope ; anterior margin rounded, 
passing gradually into the convex ventral margin; posterior margin rather short, 
oblique, more or less truncated, forming a rounded angle with the nearly straight 
and ventrally sloping postero-dorsal margin. Umbones rather prominent, curved 
inwards and slightly backwards. Postero-dorsal part of valves compressed, some- 
times with a small carina. Surface with numerous small concentric growth-ridges. 
Measurements : 
(1) (2) (3) 
Length : 68 : 64. : 49 mm. 
Height 2 52 : 46 : BS) ey 
Thickness : 30 28 ; ieee 
(1—3) Speeton. 
Affinities—It 1s probable, as maintained by Harbort,! that Thracia striata, 
Weerth,” is not specifically distinct from 7. Phillipsi. 
Remarks.—The greater part of the shell has disappeared from most of the 
examples found at Speeton, and usually some part of the margin of the cast has 
also been lost. I have not seen sufficient examples to enable me to determine 
whether the variation of this species in England is as great as im the case of the 
specimens found in Schaumbure-lippe and described by Harbort. 
T'ype.—F rom Speeton, in the York Museum. 
Distribution.—Speeton Clay (zone of Belemnites jaculum) of Speeton. 
Turacia RotuNDatA (Sowerby), 1836. Plate XXXIX, fig. 10a, bd. 
1836. Panopma rnotunpata, J. de C. Sowerby. Trans. Geol. Soc., ser. 2, vol. iv, 
pp. 129, 337, pl. xin, fig. 2. 
1850. Lyons1a susprorunpata, A. d’Orbigny. Prodr, de Pal., vol. ui, p. 74. 
1854. Myacrttes rotunpata, J. Morris. Cat. Brit. Foss., ed. 2, p. 214. 
1865. THracrta susrorunpata, F. J. Pictet and G. Campiche. Foss. Terr. Crét. 
Ste. Croix (Matér. Pal. Suisse, ser. 4), p. 120. 
1870. Corimmya rorunpbata, F. Stoliczka. Paleont. Indica, Cret. Fauna 8. India, 
vol. in, p. 72. 
Description.—Shell regularly convex, oval, shghtly inequivalve and inequilateral. 
Anterior and ventral margins convex, forming a regular curve. Dorsal part of 
posterior margin oblique, forming an angle with the ventral part. _Umbones broad, 
in contact, with a narrow, sharp, curved carina extending to the posterior angle 
and lmiting a triangular, concave, postero-dorsal area, which is ornamented with 
fine ribs running parallel to the posterior margin. Sides of valves with similar 
ribs extending in a radial direction. 
1 «Die Fauna d. Schaumburg-Lippe’schen Kreidemulde’ (1905), p. 78. 
2 *Neocomsandst. im Teutoburg. Walde’ (‘ Paleont. Abhandl.’ IT, 1884), p. 40, pl. viii, fig. 10. 
Wollemann, ‘ Die Bivalv. u. Gastrop. d. deutsch. u. hollind. Neocoms’ (1900), p. 140, pl. vii, fig. 1. 
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