176 CRETACEOUS LAMELLIBRANCHIA. 



18G5. Tellina subtenuistriata, F. J. Pictet and G. Campiche. Foss. Terr. Oct. 



Ste. Croix (Mater. Pal. 

 Suisse, ser. 4), pp. 132, 

 138. 

 1870. Ajwphidesma tenuistriatum, F. Stoliezka. Palseont. Indica, Cret. Fauna 



S. India, vol. iii, p. Ill 

 (? Thracia or Tellina). 



Description. — Shell oval, of moderate convexity, nearly equilateral. Anterior 

 margin rounded ; ventral margin moderately convex ; posterior margin truncated, 

 more or less oblique, forming a blunt angle with the ventral margin, and an obtuse 

 angle with the postero-dorsal margin. Umbones rather broad, scarcely curved. 

 Postero-dorsal part of shell compressed and flattened. 



Ornamentation consists of numerous strong, regular, concentric ribs, and of a 

 few small radial ribs on the anterior part, and of a larger number on the postero- 

 dorsal region and the part just in front of it. 



Measurements : 



(1) (2) (3) (4) 



Length . 19 . 18 . 17 . 13 mm. 



Height . 13-5 . 13 . 115 . 9 „ 



(1 — 4) Blackdown. 



Affinities. — This species resembles Tellina llauliniana (d'Orbigny), 1 but possesses 

 a relatively shorter and higher shell, with a more convex ventral margin and more 

 numerous radial ribs. In form it approaches more nearly the examples from the 

 Gault of the Perte du Rhone figured by Pictet and Campiche, 3 but in the latter 

 the posterior extremity is more angular and the posterior ribs more prominent and 

 limited to the postero-dorsal region. 



T. subtenuistriata, also resembles T. subconcentrica (d'Orbigny),-' 5 but is more 

 nearly equilateral and the ventral border is more convex. 



It differs from the species from the Lower Greensand described above in the 

 flattened postero-dorsal region, the more angular posterior extremity, the smaller 

 apical angle, the larger curvature of the ventral margin, and greater relative 

 height. T. subhercynica, Maas, 4 is another similar form. 



Remarks.—- The type is somewhat imperfectly preserved, but the radial ribs on 

 the anterior and posterior parts, which are not shown in Sowerby's figure, can be 

 made out satisfactorily. The size of the apical angle and the outline of the shell 

 vary in different examples. 



1 ' Pal. Franc. Terr. Cret,,' vol. iii (1845), p. 411, pi. ccclxxviii, figs. 7-10. 

 •-' Pictet and Campiche, ' Terr. Cret. Ste. Croix ' (1865), p. 141, pi. cix, figs. 1-3. 

 :! Op. cit., p. 410, pi. ccclxxviii, figs. 1-G, and ' Prodr. de Pal.,' vol. iii (1850), p. 75. Pictet and 

 Renevier, ' Foss. Terr. Aptien ' (Mater. Pal. Suisse, ser. 1, 1856), p. 69, pi. vii, fig. 7. 

 4 ' Zeitschr. der deutsch. geol. Gesellsch.,' vol. xlvii (1895), p. 258, pi. vi, figs. 3, 4. 



