Sphenia. MOLLUSCA. MYAD^. 465 



581. L. Maris. — Retail extremity slightly produced, with 

 the dorsal margin nearly straight and subrecurved. 



Mactra hians, Putt. Dorset, 32 Don. Brit. Shells, t. cxl. Mont. Test. 



Brit. 101 L. oblonga, Turt. Biv. Brit. 64. t. v. f. 6 — In sand, be- 



yond low-water mark. 

 Length 2\ inches, breadth 5 inches; thick, coarsely striated ; it chiefly 

 differs from the last in its shortness, great breadth, the straightness of the 

 dorsal and ventral margins, and the subrecurved aspect of the posterior ex- 

 tremity. In the L. vulgaris the syphon-mark has a smooth polished border ; 

 in this species the margin is a little raised. 



The following shells, which Dr Turton has included in his genus Monta. 

 cuta, with the following character : " Shell oval or oblong, equivalve, inequi- 

 lateral ; mostly closed ; hinge with two teeth in each valve, and a cavity be- 

 tween them; lateral teeth none; ligament internal," appear to be the fry of 

 the species of the genera Mya and Lutraria, before they have begun to bur- 

 row in the sand or mud. 



1. substriata Shell oval, with obscure longitudinal ribs ; |th of an inch in 



length; Ligula substriata, Mont. Test. Brit. Sup. 25 — M. substriata, Turt. 

 Biv. Brit. 59 Adhering to Corallines and the spines of Echini. 



2. bidentata Shell ovaL, smooth, with one of the teeth oblique and spoon- 

 shaped Mya bidentata, Mont. Test. Brit. 44. t. xxvi. f. 5 — M. bid. Turt. Biv. 



Brit. 60 In cavities in old Oyster Shells. 



3. ferruginosa. — Shell oblong, slightly striated transversely, with one of the 

 teeth incurved and spoon-shaped — Mya fer. Mont. Test. Brit. Sup. 22. t. xxvi. 

 f. 2 M. fer. Turt. Biv. Brit. CO.— In Sand and Clay. 



4. oblonga Shell oblong, smooth, with all the teeth erect — M. ob. Turt. 



Biv. Brit. 61. t. xi. f. 11, 12— In Sand. 



EXTINCT SPECIES. 



1. Ij.gibbosa "Retral side widest, recurved, truncated and gaping — Sower. 



Min. Conch, t. xlii. — Oolite. 



2. L ? striata Transversely oval, compressed, concentrically striated ; pos- 

 terior side smallest, rather pointed, gaping ; beaks prominent. — Sower, Min. 

 Conch, t. Dxxxiv. f. 1 — Green Sand. 



3. L ? cariuifera. — Transversely oval, elongated, convex, longitudinally 

 striated ; posterior side smooth, bounded by an obtuse carina, truncated, its 

 edge straight Sower. Min. Conch, t. dxxiv — Lower Chalk. 



4. L ? oblata Compressed, transversely oval, with obtuse extremities 



slightly bent ; beaks prominent — Sower. Min. Conch, t. Dxxxiv. f. 3 — Lon- 

 don Clay. 



Gen. CXLI. SPHENIA. — Transverse, inequivalve, inequi- 

 lateral, open retrally ; hinge of the right valve with an 

 elevated transversely dilated tooth, of the left valve with a 

 concave tooth, and small denticle before it. — Turton. 



■ 582. S. Binghami. — Shell wedge-shaped, with the concave 

 tooth oblique and inflected. 



Turt. Biv. Brit. 36. t. cxi. f. 4, 5. and t. xix. f. 3. — In rocks, Torbay. 

 VOL. I. G g 



