34 
interrupted opaque lines very irregularly disposed 
which gives the margin a serrated appearance; beaks 
rather prominent, hinge margin nearly straight, ventral 
edce rather rounded ; gape extending the whole breadth. 
$...3. Guernsey, English channel. 
TripeE.—SOLENIDES. 
Transversely elongated, destitute of accessory pieces 
and gaping only at the sides ; ligament external. 
Genus.—SOLEN. Livy. 
Equivalve, transversely elongated. gaping at both ex- 
tremities ; beaks very small, always short : cardinal 
teeth small, varying in number, sometimes none and 
rarely a pit between them. 
* Hinge terminal, shell posteriorly truncated. 
S. Vacina. Lin. 1113.—D. p.57—Lam. {.—Don. 
4, ¢. 110.—Pen. 4. p. 83.—Mont. p. 48.—Turt. B. 
p. 79:—Subcylindrical, more compressed towards the 
truncated anterior end ; posterior end slightly oblique, 
shortest, strictured at the margin ; pale yellow longitudi- 
nally striated and annulated with brown : a single tooth 
in each valve; teeth flattened on the rubbing surface ; 
the opposite sides strengthened by arib. 1...5. Common. 
