BIVALVIA. 73 



ASTARTE ORBICULARIS, Sow. Tab. XL, fig. 33. 



ASTARTE ORBICULARIS, Sow. Min. Con., v, p. 65, tab. 444. 

 Morris. Catal., p. 187. 

 D'Orb. Prod, de Paleont., i, p. 308. 



Testa parva miborbiculari, convexa, umbonibiis medianis elevatis, lunula mat/na, valvis 

 costulis concentricis numerosis, depressis, interstiis latioribus, subcequalilus. 



Shell small, nearly orbicular, convex ; utnbones 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 A. minima, Phil., A. pisiformis, Sow., 

 A. Parkinsoni, Quenst. Of other small examples of the genus, A. pisum, Kock and 

 Dunker, and A. Pontonis, Lye., are much less orbicular, and have more prominent costae ; 

 A. mediolfevis, Buv., has the ornamentation of a similar character, but the figure is ovately 

 trigonal, and therefore sufficiently distinct. 



Geological Positions and Localities. The 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). 



ASTARTE POLITULA, Sean. Tab. XXXV, fig. 16. 



ASTARTE POUTULA, Bean. Mag. Nat. Hist., 1839. 



% 



Testa suborbiculari, convexo-plana, umbonibus antemedianis parvis, acutis, incurvis, 

 maryine cardinali curoato, fossa ligamenti, anyuxto, elonyato, maryine antico subrecto 

 lunula lanccolata, Icviter excavate ; valvis striis rcyularibits tenuissimis concenfricis, inferior? 

 irrcgdariter 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 ; lunule lanceolate and slightly excavated, its 

 margins subacute ; the surface of the valves with very fine, regular, concentric situations ; 

 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 



10 



