20 



This fhell has been confidered as an intermediate link 

 between the Mya and Solen, but its general habit is more 

 nearly allied to the former. It is found in the Mediterrayiean, 

 and fometimes on the coaft oi France and Spain, 



Decussata. Shell ovate, white, with irregular concentric ridges, de- 

 Tab. 28, f. 1, cuflated by regular longitudinal ftrice, forming tubercles at 

 the anterior end ; tlie margin undate : umbo obtufe, recurved, 

 and placed nearefl; to one end. Infide fmooth, white, with 

 a tongue Ihaped cicatricula, running from the longed fide 

 into the middle : in one valve a broad ere6l tooth ; in the 

 other a projecting lamina, with a fmall indenture for the 

 reception of the tooth of the oppofite valve/ Length nearly 

 half an inch ; breadth rather more. 



The irregular growth of this fliell, and its general ap- 

 pearance, fomewhat refembles a variety of Donax ims, but 

 it is perfe6lly diftindl, and ib a new and rare fpecies from the 

 Frith of Forth. 



Pholadia. In the former part of this work it has been remarked that 



p. 28. & ti^e chamber in which this fhell is Icxiged, is frequently linetl 



p. 559. ^jfi-i fi^g[| lii^g t}^at; of the Teredines. This in fome inttances 



is not lefs than half a line in thicknefs, and is < ompofedof 



many lamince ; iometimes thefe cafes protrude a quarter of 



an inch or more beyond the iurface of tlie Itone, in form of 



a 



