84 EOCENE MOLLUSCA. 
7. Arca cLosutosa (?), Deshayes. Tab. XV, fig. 9, a, 6. 
ARCA GLOBULOSA. Desh. Coq. Foss. des Env. de Par.,t. i, p. 209, pl. 33, figs. 4—6, 1824. 
Spec. Char. “A. testa ovato-oblongd, brevi, gibbosd, globulosd, subcordatd, inequilaterali, 
obliquatd, striatd, striis alternis minoribus, levigatis ; cardine arcuato, multidentato (?) ; 
margine crenato.”—Deshayes. 
Shell ovately oblong, short, tumid, or somewhat globular or gibbous, inequilateral, 
oblique, and striated; strize alternately large and small; dental margin slightly curved ; 
ventral margin deeply crenulated. 
Length, th of an inch; eight, th of an inch. 
Locality. Wighcliff, Barton. 
This is not particularly rare. I have referred it, with considerable doubt, to the Paris 
Basin shell. It may possibly be a variety, subglobulosa. 
On comparison with French specimens, I find that the English shell is rather smaller, 
less quadrate, or more rounded on the siphoni-lateral margin; and the dental area in the 
French shell is longer, and furnished with more numerous teeth, 17, 18 (Desh.); our 
specimens have four denticles on one side of the umbo and five on the other; those on the 
siphonal side are much inclined, almost parallel with the margin at the extremity, and, 
from the comparatively great depth of the valve, I imagine that our shell is a full-grown 
species, and not the fry of a larger one. The sculpture on the exterior resembles that 
upon 4. scapulina, the rays being alternately one large and one small; the smaller rays 
are nodulous, and the interspaces are decussated, the lines of growth being large, promi- 
nent and regular, thickening periodically the smaller rays; but the larger rays are nearly 
smooth. ‘There appears to be in this species a small triangular fossette beneath the umbo, 
like that in 4. /evigata, dividing the connector into two different arrangements, as in 
Limopsis. 
8. Arca Impouita, J. Sowerby. Tab. XV, fig. 4, a, 0. 
Arca IMpoLita. J. Sow. Geol. Trans., 2nd ser., vol. v, p. 136, pl. 8, fig. 10, 1834. 
— _— Morris. Catal. Brit. Foss., p. 185, 1854. 
Spec. Char. A. testa oblongd, convead, tumida, levigatd, glabra ; valdé inequilaterali, 
pedi-regione brevi, rotundatd ; siphoni-regione sub-quadratd ; marginibus intis integris ; 
dorsali et ventral sub-parallelis. 
“'Transversely oblong, very convex; marked with longitudinal rows of punctures ; 
anterior portion small, rounded ; posterior rounded ; front parallel to the hinge-line; shell 
thin.” —J. Sowerby. 
