17 
Lu c i n a , Bruguibres. 
Gen. Char. A more or less orbicular and in- 
equilateral, equivalved, bivalve: two di- 
verging teeth, of which 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. 
