MACTRA. 83 



between them ; the lateral ones depressed : length two 

 lines ; breadth three. 



The internal toothed margin distinguishes this species 

 from all its tribe. 



Devonshire coast : very rare. v. m. 



9. Mactra Listen. Lister s Mactra. 



Lister, pi. 253. f. 88 Da Costa, pi. 13. f. 1 Dorset Cat, 

 pi. 7. f. 1. 



Tellina plana. Donovan, pi. 64. f. 1. 



Shell oval-oblong, slightly triangular, thin, fiat, semi- 

 transparent, not polished, finely wrinkled transversely, 

 somewhat sloping to the cartilage edge where it gapes a 

 little : color pale russet-brown, sometimes dirty white, 

 blueish, or inclining to black, often marked with transverse 

 bands ; inside smooth, white, glossy, with a plain margin : 

 beaks small, central ; hinge with a large triangular cavity ; 

 the primary teeth small, a single one in one valve locking 

 into a cloven one in the other ; lateral teeth none : length 

 about an inch and a half $ breadth nearly two inches. 



Whether the M. Listeri and M. piperata of Gmelin be in- 

 dividually the same, as Mr. Dillwyn supposes, we are un- 

 able to determine ; but have chosen to retain the former 

 denomination, as being so well known and so unexception- 

 ably appropriate, in preference to the uncouth name adopt- 

 ed by Mr. Dillwyn from M. Poiret, whose Travels he has 

 quoted, but not admitted into his catalogue of authors. 



At the mouths of rivers, v. v. 



10. Mactra minutissima. Minute Mactra. 



Montagu, Svppl. p. 37- 



Shell white, nearly smooth, somewhat triangular, smooth 

 within with a plain margin : beaks prominent, strong ; 

 hinge with two primary teeth in one valve, separated by a 

 cavity for the reception of a single tooth in the other. 



Except for its triangular outline this species has a close 

 alliance to the genus "Tellina. It differs from M. triangu- 

 laris, in its size, which is little more than a line long and 

 two broad, in the teeth, and in the want of the notched 

 ni-M'sin. 



Devon coa^t. and Dublin bay. v, v, 



11. Mactra 



