BIVALVIA. 73 
ASTARTE ORBICULARIS, Sow. Tab. XL, fig. 33. 
ASTARTE ORBICULARIS, Sow. Min. Con., vy, p. 65, tab. 444. 
_ _ Morris. Catal., p. 187. 
— — D’ Orb. Prod. de Paléont., i, p. 308. 
Testa parva suborbiculari, convexa, umbonibus medianis elevatis, lunula magna, valvis 
costulis concentricis numerosis, depressis, tnterstiis latioribus, subequalibus. 
Shell small, nearly orbicular, convex ; umbones mesial and produced ; lunule distinctly 
marked, rounded, the surface with numerous (about twenty) depressed, narrow, con- 
centric little ribs, separated by somewhat wider and nearly equal spaces, upon the posterior 
side the ribs are slightly undulated. 
The little ribs are strongly marked upon the sides, but much less so upon the middle 
of the valve, and are scarcely to be distinguished upon the umbones; they are so delicate 
that the surface appears plain without the aid of a magnifier; this latter feature will 
serve to distinguish it from other small species, as 4. minima, Phil., 4. pisiformis, Sow., 
A. Parkinsoni, Quenst. Of other small examples of the genus, 4. pisum, Kock and 
Dunker, and 4. Pontonis, Lyc., are much less orbicular, and have more prominent coste ; 
A. mediolevis, Buv., has the ornamentation of a similar character, but the figure is ovatelv 
trigonal, and therefore sufficiently distinct. 
Geological Positions and Localities. 'Yhe upper beds of the Great Oolite near Bath, 
where it appears to be not uncommon; also upon the same horizon at Ancliff, Wilts. 
Luc (Calvados). ; 
AstarvreE poLituLa, Bean. Tab. XXXV, fig. 16. 
ASTARTE POLITULA, Bean. Mag. Nat. Hist., 1839. 
Testa suborbiculart, convexo-plana, umbonibus antemedianis parvis, acutis, incurvis, 
margine cardinal curvato, fossa ligament, angusto, clongato, margine antico subrecto 
lunula lanceolata, leviter excavato ; valvis striis regularibus tenuissimis concentricis, inferiore 
irregulariter plicatis. 
Shell suborbicular, rather depressed ; umbones anterior to the middle of the valves, 
small, acute, incurved; hinge-border slightly curved ; ligamental groove narrow and 
lengthened ; anterior border nearly straight ; lwnule lanceolate and slightly excavated, its 
margins subacute; the surface of the valves with very fine, regular, concentric striations ; 
the lower portion of the surface is destitute of striations, but has several irregular, con- 
centric plications. 
The convexity is moderate about the middle of the valves, but the test has not much 
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