118 MOLLUSCA FROM THE CRAG. 



side there is a prolonged canal with an opening for the protrusion of its foot, at 

 the base of which is a byssal gland and groove. 



This genus was proposed by Dr. Turton for the reception of two small species of 

 British shells, one of which had been previously placed in the genus Mya, and the 

 other in that of Cardium. 



The species known, belonging to this genus, are somewhat minute but elegant 

 bivalves, which in the living state are usually found located either in rocks or seaweeds, 

 though most of them are capable of spinning a byssus ; they possess a considerable 

 vertical range, some living near low water mark, while others inhabit the sea at the 

 depth of 60 fathoms. They appear to have been somewhat largely developed in the 

 Coralline Crag Period, and are invariably found free or loose in the sand, and if ever 

 imbedded it must have been in the leaves or roots of seaweed, or in some material 

 which by decomposition or disintegration has liberated them from their confined 

 position. All my specimens were found in one locality, where there is a large accumu- 

 lation of numerous small species. This genus has been obtained in considerable abun- 

 dance from the Older Tertiaries of this country, and several species enrich the Cabinet 

 of my friend F. E. Edwards, Esq. There has not been anything found in the secondary 

 Formations that can with certainty be referred to this genus, although a shell in the 

 Green-sand strongly resembles it. 



One or two species from the Crag included under this generic title possess 

 characters that will perhaps scarcely come within the range of our diagnosis. A 

 considerable variation may be observed in their dental arrangement, some being 

 furnished with two or more of these appendages, while others seem to be wholly 

 deficient, an internal ligament placed in an oblique depression appears an universal 

 character. 



1. KELLIA SUBORBICULARIS, Montague. Tab. XII, fig. 8, a, b. 



MYA SUBORBICULARTS. Mont. Test. Brit., pp. 39, 564, t. 26, fig. 6, 1803. 

 Mat. and Rack. Linn. Trans., vol. viii, p. 41, 1807. 

 Dillw. Des. Cat. Eec. Shells, p. 55, 1817. 

 TELLINA SUBORBICULARIS. Turt. Conch. Diet., p. 179, 1819. 

 AMPHIDESMA PHYSOIDES. Lam. Hist, des An. s. Vert., t. v, p. 493, 1818, fide 



G. B. Sow. 



KELLIA SUBORBICULARIS. Turt. Brit. Biv., p. 57, t. 11, figs. 5, 6, 1822. 



Flem. Brit. An., p. 430, 1828. 

 Macgill. Moll. Aberd., p. 276, 1843. 

 Thorpe. Brit. Mar. Conch., p. 51, 1844. 

 J. Sowerby. Min. Conch., t. 637, fig. 1. 

 Lovtn. Ind. Moll. Scand., p. 44, 1846. 

 Alder. Cat. Moll. North, and Durh., p. 93, 1848. 

 Forb. and Hani. Hist. Brit. Moll., vol. ii, p. 87, pi. 18, fig. 9, 



a, b, and pi. 0, fig. 4, 1849. 

 KELLIA LACTEA? Lovtn. Ind. Moll. Scand., p. 44, 1846. 



