76 SAXICAVID^E. 



Plymouth, and dredged in muddy sand off Skye, and in 

 the voes of Deal, Dourie, and Basta, Shetland, at depths 

 ranging from 5 to 40 f. (J. G. J.) ; small living speci- 

 mens were also dredged by Mr. Barlee in Loch Fyne, 

 and single valves by Mr. Hanley near the pier at Hyde 

 in the Isle of Wight; Moray firth (Dawson) ; Stone- 

 haven (Macgillivray) ; Walton-on-the-Naze (S. Wood). 

 It is a common shell in the Coralline Crag at Sutton ; 

 and Nyst found it in the corresponding formation near 

 Antwerp. M f Andrew dredged it in 40 f. off Gibraltar 

 and in Vigo Bay, Lilljeborg in 70 f. at Bergen; and it 

 has also been found at Hellebsek in Zealand. 



I hope the animal will at some future time be made 

 known. The shell may be distinguished from My a 

 Binahami bv its nacreous texture, the extreme dilatation 

 of the posterior side, and having a ligament instead of 

 a cartilage, with a different hinge. Some specimens 

 are partially incrusted by a mineral or faecal deposit, 

 showing the sedentary or inactive habits of the animal. 

 The largest in my cabinet is nearly half an inch broad. 

 Fossil specimens are rather more oblong, and the pos- 

 terior dorsal margin is straighter and less arched than 

 in recent specimens. 



If the present species, or my description of it, is com- 

 pared with Montagu's account, and with the figure 

 given by the original discoverer, Laskey, in the ' Me- 

 moirs of the Wernerian Society' (vol. i. pi. viii. f. 2), 

 their identity will, I think, be found undeniable. It is the 

 Sphenia cylindrica of S. Wood, and Saxicava fragilis? 

 of Nyst. The Mytilus carinatus of Brocchi may possibly 

 be a variety. Philippi proposed for this last and another 

 species the generic name Arcinella, which had been 

 previously used by Oken and Schumacher for two other 

 kinds of bivalve shells. 



