402 MOLLUSCA. ARCADE. Nucula. 



Length about half an inch, breadth a little more ; cuticle olive-green, with 

 yellow rays ; faintly streaked longitudinally with numerous fine lines of 

 growth. 



** Margin 'plain. 



409. N. minuta. — Shell oval, transversely striated, with the 

 anterior side produced, curved, and truncated. 



Area oblonga, striata, antice angulata, Walk. Test. Min. ii. t. cxi. f. 81, 



A. caudata, Don. Brit. Shells, t. lxxviii — A. min. Mont. Test. Brit. 



140. N. min. Turt. Biv. Brit. 178 — In deep water, not common. 



Length fths, breadth |ths of an inch ; colour white ; three or four strong 

 concentric ridges ; beak very small, turning a little towards the angulated 

 side, beneath which is a smooth depression reaching to the end. 



410. N. rostrata. — Shell oval, transversely striated, anterior 

 side produced, curved, and slightly ribbed longitudinally. 



Area rostrata, Mont. Test. Brit. Sup. 55, t. xxvii. f. 7 — N. ros. Turt, 



Biv. Brit. 178 In the Frith of Forth, Mr Laskey. 



Length half an inch, breadth three quarters ; glossy, and of a horn colour ; 

 striie fine, regular, and reflected ; from the beaks to the produced extremity 

 the striae are irregular in crossing the longitudinal ribs ; inside polished— 

 In this and the preceding species the central tooth is obsolete. 



411. N. tenuis. — Shell obliquely heart-shaped and smooth. 

 Area ten. Mont. Test. Brit. Sup. 56, t. xxix. f. 1 — N. ten. Turt. Biv. Brit, 



177 In the Frith of Forth, Mr Laskey. 



Length scarcely a quarter of an inch ; white, with an olivaceous cuticle ; 

 beaks small, slightly inflected ; hinge with six teeth on one side of the cen- 

 tral tooth, and nine on the other ; margin thin. 



EXTINCT SPECIES. 



1. N. CobbaldicB. — Transversely' obovate, convex ; surface marked with zig- 

 zag furrows, diverging over the sides; edge entire — Sower. Min. Conch. 

 t. clxxx. f. 2. — In Cray. 



2. N. lanceolata Transversely ovato-lanceolate, r smooth ; posterior side 



pointed, edge entire ; a concave deltoid space in the hinge. — Sower. Min. 

 Conch, t. clxxx. f. 1 — In Crag. 



3. N. l&vigata Transversely elliptical, convex, smooth ; posterior side 



pointed, edge entire, truncated Sower. Min. Conch, t. excii. f. 1, 2. — In 



Crag. 



4. N. similis. — Transversely obovate, depressed, obscurely striated longitu- 

 dinally ; posterior side straight ; lunette imbedded ; concave in the middle 



oblong, edge crenulated (Area nucleus, Brander, 40. f. 101.) Sower. Min. 



Conch, t. excii. f. 3, 4, 10 — London Clay. 



5. N. trigona. — Ovato-deltoid, compressed, smooth, edge crenulated, hinge 

 pit short ; lunette concave. — Sotver. Min. Conch. %. excii. f. 5. — London Clay. 



6. N. minima. — Transversely ovate, convex, transversely striated ; poste- 

 rior side acuminated ; edge entire ; lunette defined, elongated. — Sower. Min. 

 Conch, t. excii. f. 8, 9. — London Clay. 



7- N. pectinata Transversely elliptical, elongated, convex ; posterior side 



truncated ; longitudinally furrowed ; lunette imbedded, flat, cordate ; edge 

 crenulated.— Sotver. Min. Conch- t. excii. f. 6, 7— Chalk Marl. 



