73 
SOLEN, Linn. 
Gen. Char. Equivalved, very inequilateral and 
transverse, straight, gaping; at both ends ; supe- 
rior and inferior margins parallel; umbones 
nearly close to the anterior extremity. Hinge 
with one direct tooth in each valve ; ligament 
external, strong, attached to long linear fulcra. 
Epidermis thick. Muscular impressions two, 
the anterior wide, elongated, parallel to the 
fulcrum ; the other submarginal, distant from 
the beaks. Palleal impression with a deep 
sinus. Epidermis thick. 
Animal with the mantle closed except at the 
extremities. 
The division of the genus Solen of Linnseus into five genera, 
and the discovery of several species in a fossil state of four 
of the genera, have rendered it necessary to give an amended 
generic character. Amidst the various opinions as to the 
number of genera into which it should be divided, the sepa- 
ration of all those shells whose umbones are not quite late- 
ral is most general ; and next, the presence of lateral teeth 
in the hinge is allowed as sufficient to distinguish another 
group, which is however very artificial, and the genus 
Solen is thus limited as in the above Gen. Char.; but it 
may hereafter be further divided into two subgenera, one 
of them being characterized by a longitudinal furrow near 
the anterior margin, which the other does not possess. The 
