CRETACEOUS LAMELLIBRANCHIA. 
bo 
Or 
we 
Ornamentation consists of rounded ribs; those in front of the umbones are 
nearly straight and slope obliquely backwards and downwards ; those behind the 
umbones are curved and more or less nearly parallel to the posterior and postero- 
dorsal margins; near the ventral margin the ribs become more nearly concentric 
and are often less distinct (especially on the median part) than on the dorsal 
portion of the shell. 
Affinities —This species differs from G. designata (Goldfuss)' in the smaller 
curvature of the ventral margin, and in the truncated form of the posterior 
margin. It is closely allied to G. consignata, Romer,” but the anterior curvature 
of the umbones is more marked. 
Remarks.—This species has been identified by comparison with a specimen 
given me by M. Raoul Fortin from the same locality as the type. 
Type.—From the Cenomanian of Mte. Ste. Catherine, Rouen. 
Distribution.—Upper Greensand (zone of Schlanbachia rostrata) of Blackdown, 
Devizes, and near Maiden Bradley. Base of Chalk Marl of Chard.? 
Family—PLEUROMYIDA, Zittel. 
Genus—Prmuromya, L. Agassiz, 1842. 
(‘ Etudes crit. Moll. Foss.,’ Myes, p. 231.) 
Precromya Orpientana (Routllier), 1847. Plate XLITI, figs. 1, 2a—e. 
1847. Panop#a Orpiantana, C. Rouillier. Bull. Soc. Imp. Nat. Moscou, vol. xx, 
p. 407; vol. xxi (1848), p. 28], 
pl. G, fig. 24. 
Description.—Shell oval, convex, inequilateral, with a small posterior gape. 
Anterior and posterior margins rounded. Ventral margin considerably convex. 
Umbones moderately prominent, incurved. Shell depressed in front of and behind 
the umbones. Surface nearly smooth, but ornamented with linear, radial ribs, 
which are sometimes parallel, sometimes irregular; in some places the ribs are 
replaced by rows of minute tubercles. 
Affinities.—The English specimens agree closely with examples from the Lower 
1 « Petref. Germ.,’ vol. ii (1840), p. 264, pl. cliv, fig. 13. Holzapfel, ‘ Mollusk. Aachen. Kreide’ 
(Paleontographica, vol. xxxv, 1889), p. 153. 
2 «Die Verstein. d. nord-deutsch. Kreidegeb.’ (1841), p. 75, pl. x, fig. 3. Miller, ‘ Mollusk. 
Untersen. v. Braunschweig u. Ilsede’ (1898), p. 71, pl. x, fig. 7. 
3 A small specimen of Goniomya has been found in the Chalk of Trimingham by Mr. R. M. 
Brydone. 
