270 MOLLUSCA FROM THE CRAG. 



Carpenter, that gentleman seems to think it so peculiar, as almost to constitute a 

 family by itself. He describes the exterior as composed of regular prismatic cells, 

 the axes of the prisms being perpendicular to the surface, while the interior is 

 nacreous. 



No well-determined species have been met with in the fossil state in any Formation 

 older than the Paris Basin. A shell from the Carboniferous Series is described by 

 Professor M'Coy under this name ; but its claim to a place in this genus is very 

 doubtful. 



1. PANDORA IN^EQUIVALVIS, Linn. Tab. XXV, fig. 5. 



TELLINA IN^EQUIVALVIS. Linn. Syst. Nat., ed. 12, p. 1118, No. 56, 1767. 



Poli. Test. utri. Sicil., vol. i, p 39, pi. 15, figs. 5, 6, 9, and 7 

 with the animal. 



Don. Brit. Shells, vol. ii, pi. 41, fig. 1, 1800. 

 PANDORA ROSTRATA. Desk. 2d ed. Lamarck, torn, vi, p. 145. 



G. B. Sowerby. Spec. Conch. Pandora, p. 2, No. 2, figs. 79. 



Phil. En. Moll. Sic., vol. i, pi. 1, fig. 12, 1836. 



Desk. Exp. Scient. Alger. Moll., pi. 24, animal. 



Forb. and Hani. Hist. Brit. Moll., vol. i, p. 207, pi. 8, figs. 14. 



MARGARITACEA. Lamk. Hist, des An. s. Vert., torn, v, p. 137. 



Schum. Essai des Vers. Test., p. 114, pi. 4, fig. 2. 

 _ _ Turt. Brit. Biv., p. 40, pi. 3, figs. 1114, 1822. 



IN^EQUIVALVIS. Flem. Brit. Anim., p. 466, 1828. 



Spec. Char. Testa elongato-ovatd, l&vigatd, tenui fragili, incequilaterali ; later e postico 

 longiore, attenuate subrostrato, hinc in utrague valvd anyulato. 



Shell elongately ovate, smooth, thin and fragile, inequilateral ; posterior side the 

 longer, attenuated, and somewhat beaked, slightly angulated in each valve. 



Length, f inch. Height, f inch. 



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



My specimens of this species are but few, and those not in good condition. The 

 one figured has the siphonal area elongated into the form of a rostrum or beak, and 

 corresponds with what the British conchologists have considered a distinct species. 

 In the young state, as indicated by the lines of growth, the dorsal margin is more 

 convex than concave, and the shell comparatively broader, like P. Pinna, and there is 

 no appearance then of a rostrum. 



2. PANDORA PINNA, Montague. Tab. XXV, fig. 4, ac. 



SOLEN PINNA. Mont. Test. Brit., p. 566, t. 15, fig. 3, 1803. 

 PANDORA OBTUSA. Leach. Ross's Voy. Baffin's Bay, p. 174, 1819. 



