2.26 MOLLUSCA FROM THE CRAG. 



1. TELLINA CRASSA, Pennant. Tab. XXI, fig. 1, a e. 



TELLINA CRASSA. Penn. Brit. Zool., ed. 4, p. 73. 



1 Dujard. Mem. de la Soc. Geol. de France, t. 11, pi. 11, p. 258, 1837. 



Smith. Mem. Wern. Soc., vol. viii, p. 93. 

 Phil. En. Moll. Sic., vol. ii, p. 23, 1844. 



Lovtn. Ind. Moll. Scand., p. 41, No. 296, 1846. 



Sismonda. Syn. Meth. An. Inv. Fed. Foss., p. 21, 1847. 



RIGIDA. Pulteney. In Hutcben's Hist, of Dorset, p. 30. 

 SCABRA. Chemn. Conch. Cab., vol. vi, t. 10, fig. 94. 

 MACTJLATA. Adams. Linn. Trans., vol. iii, p. 252. 



Turt. Brit. Biv., p. 108, pi. 6, fig. 7, 1822. 



OBTUSA. J. Sow. Min. Conch., t. 179, fig. 4. 



Nyst. Coq. Foss. de Belg., p. 106, pi. 5, fig. 1, 1844. 

 SUBROTUNDA. Phil. En. Moll. Sic., vol. i, pp. 29 and 255, 1839. 

 VENUS CRASSA. Gmel. Syst. Nat., p. 3288. 

 PECTUNCULUS PLANTJS CKASSTJS. List. Hist. Conch., fig. 136, 1687. 



DEPRESSION. Da Costa. Brit. Conch., p. 194, t. 13, fig. 4, right-hand figure. 

 ARCOFAGIA CR.ASSA. Brown. Illust. Brit. Couch., pi. 16, fig. 8, 1827. 

 OVATA. Id. Illust. Brit. Conch., pi. 16, figs. 9, 10. 



Dale. Hist, and Antiq. of Harwich, t. 11, fig. 13, 1730. 



Spec. Char. Testa crassd, ovato-ellipticd, transversd, depressd, utrinque cequaliter 

 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 lamellae. 



Length, 2 inches. Height, \\ inch. 



Locality. Cor. Crag, Button. 



Red Crag, Sutton, Walton Naze. 



Mam. Crag, Chillesford. 



Clyde Beds. (Smith.) 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 striae ; 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 T. subrotunda, Des. 'Coq. Foss. des Env. de Paris/ torn, i, p. 81, pi. 12, 

 figs. 16, 17, strongly resembles this species, and is considered as identical by Philippi; 



