436 mactrid^:. 



which are bluntly crested or pointed in the middle, the an- 

 terior lateral being longer than the other ; in the left valve a 

 minute erect cardinal which fits into those of the right valve ; 

 lateral teeth in this valve ridge-like and obscure : inside 

 nacreous, minutely and irregularly striated towards the margin : 

 pallial scar distinct; sinus rather long and tongue-shaped: 

 muscular scars slight, of an irregular shape. L. 0*4. B. 0*8. 



Habitat : Sparingly distributed on all our sandy 

 coasts, from the Shetland to the Channel Isles, in 3-87 

 fathoms. Fossil in the Clyde beds and Coralline Crag 

 (Smith and Wood) ; Sicilian and Calabrian tertiaries 

 (Philippi). It is extensively diffused both north and 

 south, from Iceland (Steenstrup) to the iEgean (Forbes), 

 at depths varying from 8 to 150 fathoms. 



The animal is lively, and active by fits and starts — 

 now and then darting out and twisting about on all 

 sides its long and slender foot, as if for the purpose of 

 burrowing. The shell, which is of an elegant shape, is 

 frequently found in the stomachs of haddocks, as well as 

 of the common plaice and other fiat fish. 



The Erycina angulosa of Bronn is probably identical 

 with this species. 



2. S. ni'tida* Muller. 



Mya nitida, Mull. Prodr. Zool. Dan. p. 245. Syndosmya intermedia, 

 F. &H. i. p. 319, pi. xvii. f. 9, 10, and (animal) pi. K f. 5. 



Body clear white : mantle fringed with numerous short 

 cilia : tubes very long, closely ammlated or marked across with 

 slight rings of a dusky hue, resembling those in certain species 

 of Tubularia ; incurrent tube cylindrical; excurrent somewhat 

 longer and tapering to a fine point ; both are covered with a 

 few scattered papillae : foot large and extensile. 



Shell similar in many respects to that of S. prismatica, 

 but longer in proportion to its breadth, so as to be rather 

 oval than oblong : the surface has in front and at the sides 



* Glossy. 



