mactridjE. 411 



to be a West-Indian shell; and there is no satisfactory 

 evidence that it has ever been found in the British seas, 

 much less in the Firth of Forth. 



D. denticulatus (Linne) is West Indian, and likewise 

 " spurious." Chemnitz called it D, punctata, Da Costa 

 Cuneus truncatus, and Donovan D. crenulata, the last 

 alleging that it was "very common on the western coasts 

 of England and also on those of Ireland and Scotland." 

 Linne assigned to this species the Mediterranean as a 

 habitat, on the authority of F. Logie, one of his pupils ; 

 Payraudeau and others afterwards recorded it from the 

 same locality ; and the Rev. R. T. Lowe lately observed 

 specimens at Mogador. It is the " Nusar " of Adanson. 



Family XV. MAC'TRID^, (Mactradse) Fleming. 



Body oval or oblong : mantle closed to some extent, fringed 

 at its edges : tubes more or less elongated, in some genera 

 united and in others separate : gills consisting of an unequal 

 pair on each side : foot tongue-shaped and flexible. 



Shell equivalve, triangularly oval or oblong, sometimes 

 gaping at the posterior end or at both ends, usually sculptured 

 by fine concentric strise : epidermis fibrous : ligament double, 

 the external one slight and placed on the larger side of the 

 shell, and the internal one (or cartilage') solid, placed on the 

 same side, and occupying a large pit or cavity in the hinge : 

 teeth, two cardinals in each valve (except in Scrobicularia, 

 which has only one in the left valve), besides more or less dis- 

 tinct laterals : pallial scar sinuated : muscular scars deep or 

 distinct. 



The present volume will conclude with this family, 

 being the last of those which have the mantle open. It 

 is remarkable for possessing a double ligament, one ex- 

 ternal and the other internal ; but otherwise it is not of 

 much repute, whether we look to the shape or to the 

 colour of the shell. Usually the former is short or 

 stumpy, and the latter pale and unattractive. It is, 



t2 



