212 CRETACEOUS LAMELLIBRANCHIA. 



Non. 1869. Janiea quadricostata, E. Favrc. Moll. Foss. de la Craie de Lemberg, 



p. 155. 



— 1876. Vola quadricostata, D. Brawns, Seuou. des Salzberges (Zeitschr. f. d. 



gesammt. Naturwiss., vol. xlvi), 

 p. 388. 



— 1877. Janira quadricostata, A. Peron. Bull. Soc. geol. de Frauce, ser. 3, vol. v, 



p. 502. 



— 1889. Vola quadricostata, E. Holzapfel. Die Mollusk. Aachen. Kreide (Palaeon- 



tographica, vol. xxxv), p. 237, 

 pi. xxvi, fig. 20. 



— — — — 0. Griepenkerl. Seuou. vou Konigslutter (Pala3ont. 



Abhaudl., vol. iv), p. 48. 



— 1892. Neithea quadricostata, K. Futterer. Kreidebild. des Lago di Santa 



Croce (Palseout. Abhaudl., vol. 

 vi), p. 80, pi. iii, fig. 6. 



- 1894. Vola quadricostata, A. Hennig. Om Ahussandst. (Geol. Foreu. i Stock- 



holm Forhandl., vol. xvi), p. 520. 

 B. Lundgren. Mollusk-faunan i Mammillat. och 

 Mucronata zouerua (K. Svenska 

 Vet.-Akad. Handl, N. F„ vol. 

 xxvi, No. 6), p. 44. 



- 1895. F. Vogel. Hollandisch. Kreide, p. 25. 



— 1896. A. Rutot. Bull. Soc. Beige de Geol., etc., vol. x, 



p. 30. 



- 1901. H. ImlceUer. Kreidebild. am Stallauer Eck, etc. 



(Palseontographica, vol. xlviii), 

 p. 31, pi. i, figs. 8, 9, 



Description. — Shell large, ovate, rounded ventrally, more or less pointed 

 dorsally, nearly equilateral; postero-dorsal a little longer than the antero-dorsal 

 margin. Hinge-line long ; ears large. 



Right valve convex. Umbo prominent, incurved. Length of valve either 

 equal to or slightly less than its height; greatest length at about the middle of 

 the valve. Usually with twenty-one (occasionally twenty-four) ribs, which curve 

 slightly outwards; all are strong and rounded, with slightly narrower furrows 

 separating them. Six of the ribs are rather larger than the others, and project 

 slightly at the ventral margin, forming angles, between which the margin of the 

 valve is straight or slightly concave. The interspaces between the six main ribs 

 are flattened, and in each, three (rarely four) smaller ribs occur; these are of 

 nearly equal size, but the middle is sometimes slightly larger than the lateral. 

 Occasionally tin's regularity in the ribs is partly lost owing to the stronger ribs 

 being more numerous and the smaller ribs fewer than usual. Both ribs and 

 furrows are crossed by numerous, very fine, regular concentric ridges, which 

 .ire continued on to the areas. Antero- and postero-dorsal areas of fairly large 

 size and sloping outwards — the former a little smaller than the latter. Antero- 



