130 MOLLUSCA FROM THE CRAG. 



MoNTACCTA FEERUGINEA. Thorpe. Brit. JIar. Conch., p. 52, fig. 10, 1S44. 



— OVATA. S. Wood. Catalogue, 1840. 



— TENELLA? Lovin. Iiid. JMoU. Scant!., p. 43, 1846. 

 Tellimva OVATA. Brown. Illust. Brit. Conch., pi. 14, figs. 20, 21, 1827. 



— ELLIPTICA. Id. - . . pi. 14, figs. 17, 18, „ 



— GLABRA. Id. . . - 2d ed., p. 107, pi. 42, figs. 20, 21. 



— OVATA. Smith. Mem. Wern. Soc, vol. viii, p. 41, 1838. 

 Erycina ferkuginosa. liecltic. Rev. Zool. Cuv., p 332, 1844. 



S/jec. Char. Testa transversa, ellipticd, convexd, tenui, Icevitjatd vel concentrice striata , 

 antice longiore, postice subattenuatd ; marline dorsall et ventral i leviter arcuatis. 



Shell transverse, elliptical, convex, thin, smooth, or striated concentrically, 

 anterior side the longer, posterior slightly attenuated, dorsal and ventral margins 

 gently curved. 



Length, \ an inch. Height, \ of an inch. 



Locality, Cor. Crag, Sutton. Recent, Britain and Scandinavia. 



This is not an abundant slicll in my Cabinet, a few specimens however are 

 sufficiently perfect to be fairly compared with tlie recent British shell, and I believe 

 the dififerences are not more than may be considered as local variations. 



Our shell is very transverse, having a length about twice that of its height, 

 the anterior side occupying about three fifths of the entire shell ; the posterior 

 side is rather more pointed than in the recent specimens I have compared with, 

 but in Messrs. Forbes and Hanley's description of the living species, it seems 

 to have a considerable range in variation, occasionally resembling our own shell 

 in that character, which appears to be its only difference : in perfect specimens 

 the exterior is covered with regular concentric striae, and the hinge is formed of an 

 internal ligament of an angular form, deeply inserted, and sloi)ing towards the pos- 

 terior side ; a portion of the ligament was probably seen externally, as a small sinus 

 is formed in the umbo, through which it might have extruded, this pit, or support 

 for the ligament is thickened at tlic edges, and elevated behind, so as to produce a 

 sort of denticle in the left valve, and immediately before it is a distinct though not a 

 prominent tooth, the same appearances are exhibited in the right valve, in which the 

 tooth is rather more elevated. There are large adductor muscle marks of an ovate 

 form, and the impression by the mantle is entire. 



The animal of this species has been recently examined by Mr. Alder, who has 

 published his observations in the ' Ann. and Mag. of Nat. Hist.' for the present year, 

 where he has pointed out a peculiarity in the mantle on the anterior side, by which it 

 appears, he says, to connect the open-lobed form in Lepton with the anterior tubular 

 extension of that organ in Kcllia. 



Vcr\' extraordinary forms arc assumed by the fleshy covering or mantle in many 

 of the animals of this group, presenting us with distinctions so apparently anomalous 

 as to entitle them, if distinguished by that organ alone, to be removed to very distant 



