BIVALVIA. 85 
giving a more ovate form to the outline. It has a rather narrow row of denticles on 
both sides, those upon the anterior are from ten to twelve in number, with about six 
or eight upon the shorter or posterior side. A shell somewhat resembling this is 
found in the Upper Marine, in Headon Hill, being free from crenulations at the 
margin, and is also a thin shell, with a similar ovate contour, though seemingly 
rather more pointed at the posterior extremity, but my specimens of the Eocene 
fossil are scarcely in a sufficiently good state of preservation for a fair comparison. 
A specimen of this species, found at Bridlington, was, obligingly forwarded to me 
for examination by Mr. Leckenby. 
4. NucuLa Nuc eEus, Linneus. Tab. X, fig. 6, a—é. 
Arca NucLEus. Linn. Syst. Nat., ed. 12, No. 184, p. 1143, 1767, not Brander. 
— a= Chem. Conch. Cab., t. vii, p. 241, t. 58, fig. 574, 1784. 
— — Don. Brit. Shells, vol. ii, pl. 63, 1801. 
— — Broc. Conch. Foss. Subap., vol. ii, p. 480, 1814. 
— — W. Wood. Ind. Test., p. 47, pl. 10, fig. 42, 1825. 
Nuctta Nucuevs. Turt. Brit. Biv., p. 176, t. 13, fig. 4, 1822. 
— — S. Wood. Mag. Nat. Hist., New Series, vol. iv, p. 294, pl. 14, fig. 1, 
1840. 
— _ Thorpe. Brit. Mar. Conch., p. 105, p. 74, 1844. 
= — Lovén. Ind. Moll. Seand., p. 34, 1846. 
= — Forb. and Hanl. Hist. of Brit. Moll., vol. u, p. 215, pl. 47, figs. 7, 8, 
1849. 
—  mMarGAriTacEa. Lam. Syst. des An. s. Vert., p. 115, 1801 (mostly). 
= = G. B. Sowerby. Genera, No. 17, fig. 7. 
— a De Blaimv. Malac., pl. 75, fig. 5, 1825. 
— — ? Bast. Mem. de la Soc. d Hist. Nat., t. 2, p. 78, No. 2, 1825. 
_ -~ ‘Payr. Cat. Moll. Cors. p. 64, 1826. 
= — Brown. Illust. Conch. Gr. Brit., pl. 25, fig. 12, 1827. 
= — Dubois. Conch. Foss. Wolhyn. Podol., p. 66, t. 7, figs. 35, 36, 
1831. 
—_ — Goldf. Pet. Germ., vol. ii, p. 158, t. 125, fig. 21, a—d. 
— —_ Phil. En. Moll. Sic., vol. i, p. 64, t. v, fig. 8, 1836. 
— _ Bronn. Leth. Geol., yol. ii, p. 929, t. 39, fig. 5, a—e, 1838. 
oe — Swains. Malac., p. 382, fig. 125, f—g, 1840. 
_ — G. B. Sow., Jr. Conch. Man., fig. 137, 1842. 
—_ — Forbes. Report on #gean Invert., p. 180, 1843. 
— ; — Sism. Syn. Meth. An. Inv. Piedm. Foss., p. 15, 1847. 
—  arGENTEA? Brown. Illust. Conch. Gr. Brit., pl. 25, figs. 14, 15, 1827. 
GLYCIMERIS ARGENTEA. Da Costa. Brit. Conch., p. 170, pl. 15, fig. 6, 1778. 
DonaX ARGENTEA. Gmel. Syst. Nat., p. 3265, 1788. 
Ency. Meth., pl. 311, fig. 3, a—d. 
Spec. Char. Testa obliqud, ovatd, transversd, subtriangulari, levi, aut obsolete striata ; 
dentibus cardinalibus acutis ; margine crenulato. 
Shell obliquely ovate, transverse, slightly triangular, smooth or obsoletely striated ; 
hinge with numerous, sharp, and erect teeth ; margin crenulated. 
