BIVALVES — SOLEN. 19 



SOLEN. — Razor-sheath or Knife-handle. 



DESCRIPTION OF PLATE V. 



Diy. I. —Fig. 2. S. truncatus. Div. II. — Fig. 4. S. vespertinus. 



Fig. 3. S. vagina. Fig. 5. S. radiatus- 



Drv. II. — Fig. 1. S. oriens. Fig. 6. S. occidens. 



Shell bivalve, oblong, open at both ends: hinge with a subnlate re- 

 flected tooth, often double, and not inserted in the opposite valve. 



OF this g-enus there are thirty-five species, which 

 vary exceeding-ly in form and general appearance. 



The principal characteristic is derived from the 

 hinge, usually supplied with one subulate tooth, 

 which is often found double, though not always 

 inserted in the opposite valve. 



Most species of the Solen are covered with a 

 thin cuticle or epidermis, which renders the colors 

 beneath more or less obscure. 



The first division consists of those species, whose 

 breadth greatly exceeds their length; and the second, 

 of those that are oval or oblong. 



In some species of the first division, as in S.siliqua 

 S. vagina, &c. the breadth of the shell is nearly seven 

 times its length, giving it a resemblance to the handle 

 of a knife, or sheath of a razor; and some are curved 

 or bent like the scabbard of a scimitar. The shells 

 of this division have both ends invariably open. 



The greater proportion of the shells of this genus 

 are found in the European and Northern seas. The 

 C2 



