BIVALVIA. 247 
Locality. ? Cor. Crag, Sutton. 
Red Crag, Bawdsey, Sutton, Woodbridge. 
Mam. Crag, Bramerton, Chillesford. 
Clyde Beds. Recent, Finmark, Britain. 
The name of ovalis is selected in preference to that of dudia, as being best suited 
to the character of the species, both having been proposed at the same time. 
A considerable range in variation is observable in the numerous specimens found 
in the Red Crag, some of which very closely approach J. solida, so much so that I 
was induced to consider it in my ‘Catalogue’ only as a variety, more especially as in 
this, when perfect, the dorsal portion is marked with ridges such as are supposed to be 
a good distinguishing character for that species. The principal difference appears to 
be a greater solidity of substance in the one so named, and the other is of course 
thinner. Our Red Crag fossil has the exterior covered with very fine, close-set, and 
rather irregular strize, while upon the upper or dorsal portion it is more strongly ridged 
than is usual in the recent shell. The variety JZ. dudia is less elliptical, with the dorsal 
portion ridged, connecting it in that character with JV. solida, from which it differs only 
in being rather more oval and thinner. 
In the Red Crag this is one of the most abundant shells, and may be obtained 
in most localities; but I have never found it at Walton-on-the-Naze. 
9. MacTRA suBTRUNCATA, Da Costa. Tab. XXIV, fig. 3, a, 4. 
TRIGONELLA suBTRUNCATA. Da Costa. Brit. Conch., p. 198, 1778. 
Macrra suprruncata. Mont. Test. Brit., p. 93, and Sup., p. 37, pl. 27, fig. 1. 
— — Lovén. Ind. Moll. Seand., p. 45, 1846. 
= _ Forb. and Hanl. Hist. Brit. Moll., vol. i, p. 358, pl. 21, fig. 8; 
pl. 22, fig. 2; and pl. 1, fig. 3, 1848. 
— — ? Midd. Malac. Rossic., p. 581, t. 18, figs. 11—13. 
— — Stsmonda. Syn. Meth. Anim. Invert. Ped. Foss., p. 22, 1847. 
— cunpata. J. Sow. Min. Conch., t. 160, fig. 7, 1817. 
= — Woodw. Geol. of Norf., p. 43, t. 2, fig. 10, 1833. 
— Evxintca? Krynichi. Bull. des Not. de Moscou, No. 11, p. 63, 1837. 
— umepata. Menke. Fide Lovén. 
SPISULA suBTRUNCATA. Gray. Mag. Nat. Hist., new series, p. 374, 1837. 
Spec. Char. Testa ovato-triangulari, vel cuneiformi, inequilaterali, crass; anticé 
breviore subtruncatd ; postice producta, angulatd ; dentibus lateralibus perpendiculariter 
striatis ; margine ventrali convexiusculo. 
Shell ovately triangular or obtusely wedge-shaped, inequilateral, thick; anterior 
side the shorter, and roundedly truncate; posterior side produced, and angulated ; 
beaks slightly prominent; lateral teeth perpendicularly striated; ventral margin 
slightly convex. 
