32 CRETACEOUS LAMELLIBRANCHIA. 



Family — ARCIDiE, Lamarck. 



Genus — Aeca, Linneeus, 1758 (sensu stricto). 



(' Syst. Nat.,' ed. 10, p. 693.) 



1. Lower Cretaceous Species. 



Aeca Dupiniana, cVOrbigny, 1844. Plate VI, figs. 1 a, b, 2, 3. 



1844. Arca Dupiniana, A. d'Orbigny. Pal. Fran 9. Terr. Cret., vol. iii, p. 207, 



pi. cccx, figs. 9, 10. 

 1S45. — — JE. Forbes. Quart. Journ. Geol. Soc, vol. i, p. 246. 



1850. — — A. d'Orbigny. Prodr. de Pal., vol. ii, p. SO. 



1854. — —J. Morris. Cat, Brit. Foss., ed. 2, p. 185. 



1855. — G. Cotteau. Moll. Foss. de l'Yonne, p. 86. 



1866. — — F J. Pictet and G. Campiclie. Foss. du Terr. Cret. 



Ste. Croix (Mater. Pal. Suisse, ser. 4), pt. 3, 

 pp. 438, 46S. 



1867. — — P. de Loriol. In A. Favre, Eecherch. geol. dans 



Savoie, &c, vol. i, p. 381. 

 1871. — F. Stoliczha: Palseont. Indica, Cret. Fauna S. India, 



vol. iii, p. 342 (Barbatia) . 



Description. — Shell elongate, very inequilateral, convex. Anterior margin 

 rounded. Ventral margin sinuous, roughly parallel to the hinge-line. Posterior 

 margin very oblique, nearly straight, forming sharply marked obtuse and acute 

 angles with the dorsal and ventral margins respectively. Umbones prominent, 

 moderately distant, with a prominent toothed carina extending to the postero- 

 ventral angle, and cutting off a depressed postero-dorsal area. Hiuge-line long. 

 Hinge-area rather large. Ornamentation consists of numerous fine radial ribs — 

 more prominent at the anterior end — crossed by concentric growth-lines. Pos- 

 tero-dorsal area with four strong radial ribs which project posteriorly, giving a 

 toothed margin. Teeth numerous, small, transverse, the terminal teeth slightly 

 oblique. 



Measurements : 



Length ......... 25 mm. 



Height 12-5 „ 



Thickness . . . . . . . 13 



