MACTRA. 177 



Type. — From Blackdown ; in the Bristol Museum. 



Distribution. — Upper Greensand (zone of Schlcenbachia rostrata) of Blackdown. 



Tellina (Linearia) sp. Plate XXVII, figs. 14 — 1(3. 



Description. — Shell oval, moderately convex, with flattened sides, nearly equi- 

 lateral. Anterior and posterior margins rounded. Ventral margin only slightly 

 curved, and nearly parallel with the dorsal margin. Umbones broad, nearly median. 

 Postero-dorsal part of valve flattened, rather large, limited by a faint carina. 



Ornamentation consists of numerous small, regular, concentric ribs, and 

 numerous small radial ribs on the postero-dorsal area and near the anterior end. 



Measurements : 



(i) (2) (3) 



Length . 17 . 15 . 14 mm. 



Height . 12 . 10 . 9-5 „ 



(1—3) Blackdown. 

 Affinities. — This species resembles T. Rauliniana (d'Orbigny), but the radial 

 ribs are much more numerous. It is also similar to the form from the Lower 

 Greensand described above, and to T. subhercynica, Maas. 



Distribution. — Upper Greensand (zone of Scldambachia rostrata) of Blackdown. 



Family— MACTRID^E, Gray. 



Genus — Mactra, Linnaeus, 1767. 

 (' Syst. Nat.,' ed. 12, vol. i, p. 1125.) 



Mactra, sp. Plate XXVII, figs. 17, 18. 



A few specimens which resemble Mactra externally, but of which the hinge has 

 not been seen, were found in the Lower Greensand (Ferruginous Sands) of Shank- 

 lin by the late C. J. A. Meyer. They are rather larger and relatively higher than 

 M. angulata, and the carina is less distinct. The surface of the shell is ornamented 

 with small concentric ribs. 



Mactra angulata, Sowerby, 1836. Plate XXVII, figs. 19—23. 



1836. Mactra ? angulata, J. de C. Sowerby. Trans. G-eol. Soc, ser. 2, vol. iv, 



pp. 241, 341, pi. xvi, fig. 9. 

 1850. Mactra angulata, A. d'Orbigny. Prodr. de Pal., vol. ii, p. 158. 



