66 CRETACEOUS LAMELLIBRANCHIA. 
whole forms a rectangular network, with pits at the intersection of the grooves. 
Teeth numerous. Margins of valves smooth. 
Measurements : 
(1) (2) (3) 
Length . 25 20) 15°5 mm 
Height . : 21-5 i8 : : 13 ss 
Thickness 21 Ws ~~ ; Wi 
(1) and (8) from Ball Wood. (2) from Maiden Bradley. 
T'ypes.—From the Cenomanian of Rouen. 
Distribution.—Chloritie Marl of Ball Wood, near Plush, and of Maiden Bradley. 
Base of Chalk Marl (zone of Schlanbachia varians) of Cerne, near Chard. 
Genus—PerctuncuLus, Lamarck, 1799. 
[‘Mém. Soe. Hist. Nat. Paris,’ p. 87.] 
1. Lower Cretaceous Species. 
PECTUNCULUS MARULLENSIS, Leymerie, 1842. Plate XIII, figs. 9a—e, 10. 
1842. PEcruncULUS MARULLENSIS, A. Leymerie. Mém. Soe. Géol. de France, 
vol. v, p. 7, pl. ix, fig. 2. 
1844. --- -- A.d’Orbigny. Pal. Frang. Terr. Crét., vol. in, 
p- 187, pl. ecevi, figs. 1—6. 
1848. a= MAROLLENSIS, H. G. Bronn. Index Paleont., vol. i, p. 938. 
1850. — MARULLENSIS, A. d’Orbigny. Prodr. de Pal., vol. 11, p. 80. 
P P1882. = — W. Keeping. Foss., &c., Upware and Brick- 
hill, p. 116, pl. v, fig. 11. 
Description.— Shell of moderate size, suboval or nearly orbicular, longer than 
high, rather convex, compressed antero-dorsally and postero-dorsally. Anterior 
margin rounded, posterior slightly subtruncate. Umbones of moderate size, 
close together, nearly median. Hinge-area small. Hinge with from four to six 
oblique teeth on each side. Ornamentation consists of numerous radial ribs, which 
bear finer ribs, and are crossed by fine concentric ribs. 
Measurements : 
(1) (2) 
Length ; : : 1105) 2 k 11 mn. 
Height : ; 2 1 : : 9°D),, 
(1) and (2) from Shanklin. 
1 Dall considers that the name Glycimeris, Da Costa, should be adopted in place of Pectunculus 
or Avinea. Until the necessity for this change has been definitely shown, I prefer to retain the name 
which has been in general use for the last hundred years. Dall, ‘Trans. Wagner Free Inst. Sci. 
Philadelphia,’ vol. ii, pt. iv (1898), pp. 571, 607. Cossman, ‘ Rey. Crit. Paléozool.’ (1899), p. 66. 
