BIVALVIA. 103 
Some Eocene fossils have been figured and described by MM. Nyst, d’Archiac, and 
Bellardi, under the generic name of Stalagmium, strongly resembling aberrant forms of this 
genus ; they differ, however, slightly in the dental area, the central portion being much 
broader than in Zimopsis, where the triangular fossette has pushed forward the ligamental 
connector, so as to diminish materially the dental line beneath the umbo. In those shells 
called Stalagmium there is an absence of the external triangular fossette, the connector 
being situated in a linear depression on one side only of the umbo, differing also in that 
respect from Pectunculus, which it otherwise somewhat resembles ; the ligamental area is 
ridged or furrowed like most of the shells of this family. If these differences be con- 
sidered sufficient to constitute generic distinction, those shells must be denominated 
Stalagmium, Nyst, as the genus proposed by Messrs. Lea and Conrad is untenable for the 
American Eocene fossil, which, as before stated, is a species of Jodiola or Crenella. 
1. Limopsts eranubata, Lamarck. Tab. XVII, fig. 10, a, 4. 
e PEcTUNCULUS GRANULATUS. Lamk. Ann. du Mus., t. vi, p. 117, No. 4, and t. xi, pl. 18, 
fig. 6, a, 6. 
—_— — Desh. Coq. foss. des Envy. de Par., t. i, p. 227, pl 35, figs. 4— 
6, 1829. 
LIMopsIs — Prestwich, Geol. Journ., 1847, p. 404. 
= _ J. Sow. in Dixon’s Geol. of Sussex, pp. 93, 170, t. 3, fig. 19. 
_ _ Desh. An. sans Vert. du Bass. de Par., t. i, p. 842, 1859. 
Spec. Char. Testd orbiculatd, lenticulari, convexd ; subaequilaterali ; decussatim 
striatd ; striis longitudinalibus angustioribus granulosis ; cardine recto, umbonibus minimis ; 
marginibus obsolete crenulatis. 
Shell orbicularly lenticular, convex, slightly inequilateral, striated or radiated and 
decussated ; radiations fine and granular; hinge straight, umbones small, depressed ; 
margins obsoletely or irregularly crenulated. 
Diameter, 4 an inch. 
Localities. Bracklesham (#dwards). 
France: Grignon, Parnes, Senlis (Deshayes). 
This is a rare species in England, and found only at the above locality; it is said to 
be abundant in the Paris Basin. 
The surface of this shell is covered with fine, small, radiating striae, which are crossed 
or decussated by prominent lines of growth; the conjunction of these two lines causes an 
elevation, thus giving a granular surface to the exterior; the shell is nearly lenticular and 
equilateral, the diameter being, as near as possible, the same in each direction, though 
occasionally it is a trifle in excess in the height. The hinge is furnished with three to 
five denticles on one side of the umbo, nearly vertical, and on the other from five to six in 
a curving direction, and the interior margin is faintly and somewhat irregularly denticulated. 
