200 CRETACEOUS LAMELLIBRANCHIA. 
Prcren (Nurraea) compra (d’Orbigny), 1847. Plate XXXIX, figs. 6—10. 
1847. Janina comets, A. d’Orbigny. Pal. Franc. Terr. Crét., vol. iii, p. 640, 
pl. cccexlv, figs. 15—20. 
1850. = = =— Prodr. de Pal., vol. ii, p. 170. 
1868. — — A. Briart and F. L. Cornet. Descript. Mineralog. Géol. 
et Pal. de la Meule de Bracquegnies 
(Man. cour. et Mém. des Sav. 
ctrangers, vol. xxxiv), p. 50, pl. iv, 
figs. 23, 24. 
1870. -- — F.J. Pictet and G. Campiche. Foss. Terr. Crét. Ste. Croix 
(Matér. Pal. Suisse, ser. 5), p. 252. 
Description.—Shell small, subtriangular, much higher than long, nearly equi- 
lateral. Antero- and postero-dorsal margins long; ventral margin very convex, 
with deep incisions between the main ribs. Ears very unequal; the anterior very 
long, the posterior small. 
Right valve very convex, with a greatly incurved umbo, and five’ very 
prominent angular ribs, which are crossed by numerous fine concentric ridges. 
The main ribs are separated by broad, deep, rounded depressions in which from 
three to seven slightly raised radial ribs occur; these small ribs are flattened and 
separated by narrow grooves, and bear numerous fine ridges placed transversely. 
At distant intervals from two to four strong growth-ridges may occur. 
Left valve flattened, with five strong, rounded radial ribs separated by broad 
interspaces, both bemg crossed by fine concentric ridges. A few strong growth- 
ridges may occur. 
Measurements : 
Q) (2) (3) (4) (5) 
Length . , dé . Wey . Ilil > 10) TTL saan, 
Height . , ile , i® , dle). ay KGS, 
(1, 2) Cenomanian, Wilmington. 
(3, 4) Upper Greensand, Warminster. 
Ajjinities.—Vhis species is closely allied to Janira longicauda, d@Orbigny,’ but is 
distinguished from it by the main ribs being narrower and more angular. It 1s 
also nearly related to P. notabilis, Goldfuss,’ but differs in possessig five main 
ribs instead of six, and apparently also in being relatively higher. 
' Occasionally a sixth rib, not quite so prominent as the others, occurs near the anterior margin. 
2 «Pal. Franc. Terr. Crét.,’ vol. iii (1847), p. 639, pl. cccexlv, figs. 9—14. Geinitz, “ Das 
Elbthalgeb. in Sachsen” (‘ Paleontographica,’ vol. xx, pt. 1, 1872), p. 202, pl. xlv, figs. 16, 17. 
3 *« Petref. Germ.,’ vol. ii (1833), p. 56, pl. xciii, fig. 3. Geinitz, ‘Das Elbthalgeb. in Sachsen ”’ 
(- Palexontographica,’ vol. xx, pt. 1, 1872), p. 202, pl. xlv, figs. 10-12. 
