BARBATIA. 39 
umbones only, not well-marked. Postero-dorsal part of the shell sharply com- 
pressed. Hinge-area narrow, depressed, with close-set ligament-grooves. Orna- 
mentation consists of many equal-sized radial ribs, separated by narrow grooves, 
and crossed by less distinct concentric grooves. Occasionally smaller ribs (radial) 
appear in the grooves. On the postero-dorsal area the radial ribs are broader 
and more flattened. 
Measurements : (1) (2) (3) (4) 
Length. ; : . 255 . 31 . 80 . 15 mm. 
Height : . : : 15 me 28a Or ee Oli 
Thickness : : aoeeelel . ll. . — ,, 
(1) is. from Upware; (2)—(4) are from Folkestone. 
Affinities.—The shell is more rounded at the extremities and the umbones are 
less anterior than in Barbatia Raulini (d’Orbigny). 
B, marullensis is very similar to Arca Baudoniana, Cotteau;' the latter is of 
larger size, and may be only an older example of the former. It is also related to 
A. aubersonensis, Pictet and Campiche.? 
Arca Hugardiana, VOrbigny, differs in the ventral margin being oblique, and 
in having coarser radial ribs and less distinct concentric ornament. In Arca Galli- 
ennei, d’Orbigny, the umbones are more anterior (see p. 41). 
Remarks.—I have seen only two examples from the Lower Greensand, both 
from Upware, but the species has been recorded from Faringdon; it is not 
common in the Gault. The concentric ornament is not distinctly seen in the 
Upware specimens, but that is probably due to the somewhat worn nature of the 
shell. 
Types.—Specimens which agree well with the figures are in the d’Orbigny 
Collection, but I could not identify the type with certainty. 
Distribution. —Lower Greensand of Upware, and (fide Morris) of Faringdon. 
Gault (zones ili, vil, x, xi) of Folkestone.  ? Cambridge Greensand (internal 
moulds only). 
1 «Moll. Foss. de ’Yonne’ (1855), p. 86; Pictet and Campiche, “Foss. Terr. Crét. de Ste. 
Croix” (‘ Matér. Pal. Suisse,’ ser. 4), pt. 3, p. 482, pl. exxx, fig. 5. 
? Tbid., p. 433, pl. exxx, fig. 6. 
