LUCINID^. 229 



shell, as in Lasasa. The right valve has a small tuber- 

 cular cardinal tooth, a strong lateral tooth on the ante- 

 rior side, and a very indistinct one on the posterior side. 

 The hinge of Poromya is differently constructed ; and I 

 was wrong in placing the Shetland shell in that genus. 

 The form is peculiarly oblique ; but otherwise it has 

 somewhat the appearance of Axinus flexuosus. Searles 

 Wood thought his species might be the Scacchia ovata 

 of Philippi ; but I cannot agree with him that there is 

 even any resemblance between them. 



Family IX. LUCrNID^E, D'Orbigny. 



BODY nearly globular : mantle closed, except in front, where 

 there is a large opening for the egress of the foot and to admit 

 water to the gills, and also at the posterior side, where there 

 are usually one or two tubes or orifices for alimentary and 

 excretal purposes ; its edges are thickened and adhere closely 

 to the inside of the shell : gills (in all the genera but Axinus 

 and Diplodonta} one only on each side : lips (or labial palps} 

 short, and (except in those genera) two in number : foot ex- 

 tremely long, tubular and extensile. 



SHELL more or less circular, equivalve in all cases but an 

 exceptional one, nearly equilateral, of different degrees of 

 solidity, in some instances almost smooth and in others curiously 

 sculptured, completely closed : epidermis thin : beaks incurved : 

 lunule usually distinct : ligament (except in Loripes) more or 

 less external : hinge furnished with cardinal and lateral teeth 

 or with some of them, but occasionally toothless : pallial scar 

 entire : muscular scars very conspicuous, that on the anterior 

 side unusually elongated and extending far within the shell in 

 a parallel line with the front margin. 



Poli, Valenciennes, Clark, and Deshayes devoted 

 much labour to the elucidation of this family as a 

 natural group, and have published some important ob- 

 servations on the animal. But we still need further 

 information, especially as to the branchial apparatus. 



