226 MOLLUSCA FROM THE CRAG. 
1. Texitina crassa, Pennant. Tab. XXI, fig. 1, a—e. 
TELLINA cRASSA. Penn. Brit. Zool., ed. 4, p. 73. 
= — ? Dujard. Mem. de la Soc. Géol. de France, t. 11, pl. 11, p. 258, 1837. 
=— — Smith. Mem. Wern. Soc., vol. viii, p. 93. 
= — Phil. En. Moll. Sic., vol. ii, p. 23, 1844. 
— — Lovén. Ind. Moll. Scand., p. 41, No. 296, 1846. 
_ _ Sismonda. Syn. Meth. An. Inv. Ped. Foss., p. 21, 1847. 
— RIGIDA. Pulteney. In Hutchen’s Hist. of Dorset, p. 30. 
_- scaBra. Chemn. Conch. Cab., vol. vi, t. 10, fig. 94. 
— MACULATA. Adams. Linn. Trans,, vol. iii, p. 252. 
— — Turt. Brit. Biv., p. 108, pl. 6, fig. 7, 1822. 
- optusa. J. Sow. Min. Conch., t. 179, fig. 4. 
— — Nyst. Coq. Foss. de Belg., p. 106, pl. 5, fig. 1, 1844. 
—_ suBROTUNDA. P#il. En. Moll. Sic., vol. i, pp. 29 and 255, 1839. 
Venus crassa. Gmel. Syst. Nat., p. 3288. 
PECTUNCULUS PLANUS CRASSUS. ist. Hist. Conch., fig. 136, 1687. 
— pEPREssioR. Da Costa. Brit. Conch., p. 194, t. 13, fig. 4, right-hand figure. 
ArcopaGiaA crassa. Brown. Illust. Brit. Conch., pl. 16, fig. 8, 1827. 
—- OVATA. Id. Illust, Brit. Conch., pl. 16, figs. 9, 10. 
Dale. Hist. and Antiq. of Harwich, t. 11, fig. 13, 1730. 
Spec. Char.  Testd crassd, ovato-ellipticd, transversd, depressd, utrinque equaliter 
rotundatd ; latere postico breviore ; lineis creberrimis, elevatis, lamelliformibus ornata. 
Shell thick, ovate or elliptical, transverse, depressed both sides, equally rounded ; 
posterior one the shorter, ornamented with elevated close set ridges or lamellee. 
Length, 2 inches. Height, 13 inch. 
Locality, Cor. Crag, Sutton. 
Red Crag, Sutton, Walton Naze. 
Mam. Crag, Chillesford. 
Clyde Beds. (Smzith.) Recent, Britain, Coast of Scandinavia. 
This shell is rare in the Coralline, but it becomes abundant in the Red Crag, at 
Sutton, though very scarce at Walton Naze. There is a slight flexuous fold on the 
posterior margin, produced by the small sinus in the margin; and the exterior is 
covered with numerous raised ridges forming obtuse lamellae, scarcely reflexed ; be- 
tween these are fine, distinct, radiating or interstitial striz ; the right valve is the more 
tumid of the two. The palleal sinus is large and deep, with an upward direction ex- 
tending more than half way across the shell; the adductor muscle marks are deeply 
impressed, particularly the anterior one, within which is a thickened obtuse ridge from 
beneath the umbo to the lower part of the adductor. Old shells are often thickened 
on the inside, thereby deepening the muscular impressions. 
The figure of 7. subrotunda, Des. ‘Coq. Foss. des Env. de Paris,’ tom. i, p. 81, pl. 12, 
figs. 16, 17, strongly resembles this species, and is considered as identical by Philippi; 
