Astarm. MOLLUSCA. LUCINAD^. 441 



6. A. lineata Obovate, transversely depressed ; slightly truncated ; with 



a few concentric acute ridges, and many minute intervening striae upon the 

 surface ; lunette lanceolate, small ; margin entire — Sower. Min. Conch, 

 t. clxxix. f. 1. — Upper Oolite. 



"}. A. excavata Obovate, convex, concentrically costated, truncated re- 



trallv ; lunette hemispherical, excavated ; cartilage enclosed in a sulcus ; 

 margin toothed.— Sower. Min. Conch, t. ccxxxiii — Under Oolite. 



8. A. planata.—- Transversely obovate, gibbose, with small obtuse concentric 

 ridges ; edges crenulated ; lunette concave — Sower. Min. Conch, t. cclvii — 

 In Crag. 



9. A. rugata Obovate, anteriorly subtruncated, when young transversely 



costated, afterwards slightly wrinkled ; edge internally crenulated ; lunette 

 concave, obovate, pointed — Soiver. Min. Conch, t. cccxi — London Clay. 



10. A. obovata Obovate, uniformly convex, corrugated ; lunette com- 

 pressed ; anterior margin subtruncated, inner edge crenulated — Sower. Min. 

 Conch, t. cccliii. — Iron Sand. 



11. A. trigonalis Cordato-triangular, depressed, transversely sulcated ; 



beak pointed ; anterior side separated by an angle, smooth. — Sower. Min. 

 Conch, t. ccccxliv. f. 1. — Inferior Oolite. 



12. A. orbicularis. — Lenticular, with many concentric reflected lamellae up- 

 on its surface ; edge smooth. — Sower. Min. Conch, t. ccccxliv. f. 2, 3. — Upper 

 Oolite. 



13. A. pumila. — Obliquely obovate, slightly convex, with numerous con- 

 centric ridges ; edge crenated within.— Sower. Min. Conch, t. cccxliv. f. 4. 

 5, 6.— "Upper Oolite, 



14. A. striata Lenticular, transversely striated ; lunette ovate, flat, deep- 

 ly sunk, shell thick — Soioer. Min. Conch, t. dxx. f. 1 — Green Sand. 



15. A. orbicularis.-^ Lenticular, rather gibbose, concentrically furrowed ; 

 furrows small ; posterior surface plaited with an angle at its edge, lunette 

 elongated, very deep. — Sower. Min. Conch, t. dxx. f. 2. — Oolite. 



16. A. imbricata. — Cordate, orbicular, largely imbricated, convex; tooth in 

 the left valve beneath the lunette small ; lunette elongated, flat ; hinge line 



arched ; edge finely crenulated. — Sower. Min. Conch, t. Dxxi. f. 1 Suffolk, 



Crag. 



17- A. nitida — Transversely obovate, angular above, rather depressed, mi- 

 nutely sulcated near the beaks, the rest even ; beaks pointed ; lunette lan- 

 ceolate ; edge crenated — Sower. Min. Conch, t. Dxxi. f. 2. — Suffolk, Crag. 



18. A. bipartita. — Obcordate, gibbose ; six or eight large undulations upon 

 a flat space near the beak, the rest of the surface even ; beaks acute ; edge 

 toothed. — Sower. Min. Conch, t. Dxxi. f. 3. — Suffolk, Crag. 



I J). A. oblonga. — Transversely oblong, convex ; surface largely waved ; 



beaks small ; lunette cordate, pointed, concave ; edge crenated Sower. Min. 



Conch, t. Dxxi. f. 4. — Suffolk, Crag. 



Gen. CXXIV. LUCINA. — Orbicular, two teeth in each valve, 

 with lateral teeth. 



* Str'ice. concentric. 



"• 504. L. radula, — Shell with numerous raised stria?, and shal- 

 low, broad, intervening spaces. 



