BIVALVIA. 53 



Leda muoronata, Sow., Sp. Tab. VI, fig. 7. 



NucuLA MUCKONATA, Sow. Min. Con., t. 476, f. 4, 1824. 



Testa parvd suhrhomhoidali, rotundatd, convexd concentrice sulcata, postice mucronatd. 



Shell subrhomboidal, rounded, convex, concentrically sulcated, posteriorly mucronated. 



Two thirds as long as wide, very minute ; the posterior side is drawn out in the form 

 of a flattened spine, and is distinguished from the other portion of the shell by being 

 flatter. (Sowerby.) 



The figure of this shell is copied from the one given in the ' Mineral Conchology.' 



Locality. Ancliff", Wiltshire. 



Leda lachryma, Sow., Sp. Tab. V, fig. 15, 15a;. 



NucuLA LACHRYMA, Sow. Min. CoH., t. 476, f. 3, 1824. 



— — Phil. Geol. York., i, t. 11, f, 14, 1835. 



— — Goldfuss. Petref., t. 125, f. 10, 1840. 



NucuLA CAUDATA, K'och and Bunker. Beit. Nord. OoL, p. 31, t. 2, f. 7, 1837. 

 ? Leda Acasta, D'Orh. Prodrom. Paleont., i, p. 275, 1850. 



Testa ovato-subtriquetrd ventricosd, antice inflatd, postice elongatd attenuatd, mnbonibus 

 antemedianis, lunuld declivi ellipticd, marginatd, angulo cardinali ohtuso ; lateribus striis 

 concentricis remotiusculis interduni obsoletis. 



Shell ovately subtriquetral, ventricose, anterior side inflated, posterior side lengthened 

 and attenuated, umbones anterior to the middle of the shell, lunule elliptical, sloping 

 obliquely and marginated, the cardinal angle obtuse ; the sides of the shell with regular 

 concentric striations, rather remote, and faintly impressed, sometimes undistinguishable. 



The few specimens which have been obtained agree with the figure in the ' Mineral 

 Conchology,' rather than with that of Goldfuss, which is more produced posteriorly ; the 

 apparent absence of striations in the specimen figured by Sowerby has induced D'Orbigny 

 to regard the striated figure of Goldfuss as distinct, but whoever has examined the half- 

 obliterated striations of the Great Oolite specimens will be convinced of the fallacy of such 

 a distinction. The figure \ba represents the smooth variety from Ancliff, which has been 

 kindly lent to us for comparison by Mr. J. D. C. Sowerby. 



Localities. Minchinhampton and Bisley Commons; Anclifi"; it is rare. 



LiMOPSis, Schacci, 1827. 



Trigonoc^lia, Nyst, 1834. 

 Pectdnculina, D'Orbigny, 1850. 



Gen. Char. Shell smooth, transverse, ovately oblong or subquadrate, umbones mesial 

 depressed, contiguous ; hinge curved, teeth raised, numerous, minute, placed in a parallel 

 series, which is separated in its middle portion by a triangular depression. Ligament 



