414 MACTRIDiE. 



water. The former occur with Rissoa [Hydrobia] ven- 

 trosa, &c. In one large pond eels and minnows are 

 associated with S. tenuis. The shell is apt to be stained 

 in ferruginous clays." 



It is probably the Dorvillea Anglica of Leach. The 

 Erycina ovata of Philippi, from Lake Fusaro near Na- 

 ples, is closely related to the present species : Deshayes 

 named specimens of the former in the British Museum 

 " Scrobicularia piperita jun." 



B. Lateral teeth wanting. 

 5. S. pipera'ta*, Bellonius. 



Mactra piperafa, Linn. Syst. Nat. (ed. Gmelin) p. 3261. Scrobicularia 

 piperata, F. &H. i. p. 326, pi. xv. f. 5, and (animal) pi. K. f. 6. 



Body pale yellowish-white : mantle bordered by a dark line, 

 and having its edges irregularly scolloped and minutely fringed : 

 tubes cylindrical, of nearly equal length, covered with a pale 

 dirty-brown skin, tapering to their extremities, which are 

 truncate and plain (but, according to Deshayes, the orifice of 

 the excretal tube is finely ciliated, and that of the alimentary 

 tube is plain) : gills, one on each side, which is divided diago- 

 nally by a nearly central narrow groove into two subtriangular 

 portions, so as to constitute a double plate ; the}- are very 

 thick, pale-yellow, placed obliquely, delicately pectinated out- 

 side but more strongly within : palps large, thin, flat, very 

 long, triangular, broad above and pointed at their ends ; these 

 are coloured and striated like the gills : foot slightly bent, and 

 white : liver dark-green, as in the other species. 



Shell triangularly oval, flattened, usually nearly equilateral, 

 but sometimes more or less produced or elongated towards the 

 posterior end, thin, opaque, lustreless except in young and 

 fresh specimens : sculpture, numerous irregular concentric striae 

 and occasional marks of growth : colour greyish-white, often 

 stained with yellow or black from the clayey or muddy habitat: 

 epidermis slight, laminar or fibrous at the edges, glisten- 

 ing and partially iridescent : margins gently curved in front, 



* Peppery 



