MYA. 167 



the possession of Mr. Jeffreys. The characteristic trun- 

 cation of the adult is not present in the earlier stages 

 of growth, which may be seen by examining the earlier 

 concentric stages of growth in the mature valves. 



This is both a deep sea and littoral species. It is often 

 found lurking in the sand towards low- water mark, with its 

 shell embedded to the depth of three or four inches. Al- 

 though actually abundant and very widely diffused, fine 

 and perfect examples are not common in the cabinets of 

 collectors, not alone from their proneness to distortion, but 

 rather from the unpleasant and often baffling necessity of 

 digging them out from the wet spots where they are more 

 usually found. We have likewise met them, along with 

 Pholades, in chalk at Margate (S. H.), in which vicinity, 

 and also at Sandwich, the single valves are very common. 

 The species is abundant " at the mouths of rivers and in 

 bays, along with arenaria, in a mixture of gravel and mud" 

 (Alder) ; Exmouth (Clark) ; Portsmouth Harbour (Jef- 

 freys) ; Dartmouth in seven fathoms (E. F. & R. M'A) ; 

 Liverpool (M'Andrew); Scarborough (Bean); in twenty- 

 five fathoms water, five miles from land off the coast of 

 Ballaugh, Isle of Man (E.F.); Swansea (Jeffreys); Tenby 

 (Lyons) ; Anglesea in seven fathoms (M'Andrew) ; " suit- 

 able localities on every side of the Irish coast" (Thompson); 

 Frith of Forth at low water and to a depth of seven 

 fathoms (E. F.) ; Aberdeenshire (M'Gillivray) ; " Oban, 

 Ullapool, Lochs Shieldaig, and Oarron, Shetland and the 

 Orkneys" (Jeffreys and Barlee) ; dead valves in thirty-four 

 fathoms, ten miles from shore off Elgin, (R. M'A.) may be 

 enumerated among other habitats. Single valves are oc- 

 casionally met with at extreme depths. One is recorded 

 by Mr. Thompson (Ann. Nat. Hist. vol. x. p. 22), to have 

 been dredged by Caj^tain Beechey from Beaufort's Dyke at 



