17 



LuciNA, JBruguihres. 



Gen. Char. A more or less orbicular and in- 

 equilateral, equivalved, bivalve: two di- 

 verging teeth, of wliicli one is bifid, and 

 two remote teeth occur in the hinge ; the 

 ligament is external ; two remote muscular 

 impressions, the posterior one much elon- 

 gated within the entire line of attachment 

 of the mantle. 



Several of the species of this genus are ornamented 

 ■with elevated concentric lines or laminae : in some of 

 them the teeth of the hinge are partly obliterated by age, 

 in others the ligament is so deeply sunk, as to seem in- 

 ternal, but it is still visible from the outside ; the 

 posterior muscular impression, is curiously continued 

 towards the middle of the valve, beyond the part where 

 it joins the mark of the attached portion of Mantle. 

 Were this character alone to be relied upon, we might, 

 with Lamarck, admit into the Genus several shells with- 

 out teeth about the hinge ; but this plan appears not to 

 be universally approved : it is distinguished from Tellina 

 by the even margins of its valves. 



There are several fossil species described by Lamarck 

 but we have only met with one in England. 



