L88 CRETACEOUS LAMELLIBRANCHIA. 



Noil 18<J3. Vknus faba, E. Drencher. Ibid., vol. xv, p. 343. 



- 1884. Cyprimekia faba, E. Holzwpfel. Ibid., vol. xxxvi, p. 407, pi. vii, fig. 1. 



- 188i). Tapes faba, E. Hohapfel. Die Mollusk. Aachen. Kreide (Palseonto- 



graphica, vol. xxxv), p. 165, pi. xiii, figs. 7-10. 

 1897. Venus (Tapes) faba, A. Fritsch. Stud, im G-ebiete der bohin. Ki - eide- 



f or mat., vi, Chlomek. Schiclit , p. 63, 

 fig. 80. 



- 1901. F. Sturm. Jalnl). d k. preiissiscli. geol. Landesaust. 



fur 1900, vol. xxi, p. 82. 



Description.- — Shell oval, of moderate convexity, with flattened sides, con- 

 siderably inequilateral. Antero-dorsal margin short, slightly concave. Anterior 

 margin rounded, passing gradually into the slightly convex ventral margin. 

 Postero-dorsal margin long, slightly convex, with a moderate or considerable 

 ventral slope. Porterior margin short, rounded or subtruncate. Umbones small. 

 Lunule elongate, not impressed, faintly limited. Ornamentation consists of small, 

 regular, concentric ribs. 



Hinge : In the right valve the anterior and median cardinals are stout, diverge 

 slightly, and are directed forwards, and reach the lower margin of the hinge- 

 plate ; the two posterior teeth (which represent the posterior cardinal) are 

 laminar, oblique and diverging. In the left valve the anterior and median 

 cardinals are rather stout and diverge ; the posterior cardinal is slender and 

 oblique. In front of the anterior cardinal there is a concave space on the hinge- 

 plate in both valves. 



Measurements .- 



(1) (2) (3) (4) (5) 



Lengtli . 30 . 29 . 2!) 28 . 27 mm. 



Height . 25 . 24 22 . 21 22 „ 



(1 — 5) Blackdowu. 



Affinities. — Venus Archiaciana, d'Orbigny, 1 from the Senonian of Charente- 

 Inferieure, is somewhat similar in form to G. (Gyclorisma) faba, but the surface 

 of the shell is smooth. 



A species found in the Aachen Greensand has been identified by Goldfuss, 

 Holzapfel, and others with Sowerby's Venus faba, but was regarded as distinct by 

 d'Orbigny and Gr. Mailer. It differs from Sowerby's species in the greater 

 curvature of the ventral margin and the more pointed posterior extremity ; also the 

 posterior teeth in the right valve are less widely separated and are more oblique. 



Iu d'Orbigny's figure of Venus faba the ornamentation is coarser than in English 

 examples, but a specimen from the Cenomanian of Rouen (one of the localities 

 cited by d'Orbigny) differs but little in this respect from Blackdown specimens. 



Remarks. — The principal variation consists in the amount of the ventral slope 

 1 'Pal. Frany. Terr. Oct.,' vol. iii (1845), p. 449, pi. ccclxxxvi, figs. 6, 7. 



