464 MOI.LUSCA. MYADiE. Lutraria. 



4. M. suhangulata- — Rather depressed, smooth ; wider than long ; nearly 

 equilateral, oblong-ovate ; an angle from the beak to the retral margin ; ven- 

 tral margin slightly restricted. — Sower. Min. Conch, t. Ixxvi. f. 3 London 



Clay. 



5. M. lata — Ovate, depressed ; retral side acuminated and truncated, 

 slightly gaping — Sower. Min. Conch, t. Ixxxi In Crag. 



G. M ? lUerata. — Transversely oval, subequilateral, convex, smooth, thin, 

 with obtuse angularly bent ridges on the central part ; angles of the ridges 

 in a longitudmal direction. — Park. Org. Hem. iii. 196. t. xiii. f. 16. — Sower. 

 Min. Conch, t. ccxxiv. f. 1. — hiferior Oolite^ 



7. M ? scripta. — Ti'ansversely oval, subequilateral, convex, smooth, thin, 

 with oblique angularly bent ridges on the central part ; angles of the ridges 

 in an oblique direction. — Sower. Min. Conch, t. ccxxiv Inferior Oolite. 



8. M ? angulifera. — Transversely elliptical, elongated, gibbose, with oblong 

 angularly bent ridges upon the surface, retral half widest, gaping ; angles of 

 the ridges acute, in an oblique direction — Sower. Min. Conch, t. ccxxiv. f. G, 

 7. — Oolite. 



9. M ? gregaria. — Obovate, convex, subdeltoid, smooth ; retrally produced 

 and tvwwcaXed..— Sower. Mm. Conch, t. ccclxiii. — Upper fresh water Formation, 

 Isle of Wight. 



10. INI. arenaria — Soiver. Min. Conch, t. ccclxiv. and t. Dxxxi. f. 2 Nor- 

 folk and Suffolk Crag. 



11. M. depressa — Obovate, depi*essed, very slightly gaping ; anterior side 



shortest ; beaks prominent incurved, hinge-line straight, depressed Sower. 



Min. Conch, t. ccccxviii. — Middle Oolite. This is probably a Panopcea, as it 

 is stated that the ligament is external and short. 



12. M. gibbosa Obovate, transversely fun-owed, gibbose ; beaks prominent, 



incurved ; anteal side very short ; retral side rather attenuated and gaping. 

 Sower. Min. Conch, t. ccccxix. — Middle Oolite. 



13. M. p/imte.— Oblong, ventricose, straight, anterior side short, and trans- 

 versely plaited; posterior gaping, truncated.— -S'ozi'en Min. Conch, t. ccccxix. 

 f. 3 Green Sand. 



14. M ? angustata — Valves unequal; transversely elongated, thin, anti- 

 quated, irregularly compressed ; extremities obtuse, gaping ; lower edge of 

 tlie lesser valve conc&ve.—Soioer. Min. Conch, t. Dxxxi. — Upper marine For- 

 mation, Isle of Wight. 



Gen. CXL, — LUTRARIA. — Equivalve, transverse, gaping ; 

 hinge with a broad vertical plate for the cartilage, sup- 

 porting one or two teeth on its anteal margin. 



580. L. vulgaris. — Nearly equilateral, and rounded at both 

 extremities. 



Concha longa. List. An. Ang. 170. Conch, t. xiv — IMactra lutraria, 



Linn. Syst. i. 112G. Penn. Brit. Zool. iv. 92. t. Iii. fl 44. Mont. Test. 



Brit. 99. — Lutraria elliptica, Turt. Biv. Brit. Go — In sand about low- 



water mark. 



Length 24 inches, breadth 5 ; yellowish-white, with a thin close cuticle ; 



slightly striated concentrically by' the layers of growtli, with remote obsolete 



I'idges. 



1 



