NOMENCLATURE. 
33 
Valv^. Valves. 
{zquilatercz. Equilateral ; where the anterior and 
posterior sides of the valve are equal and 
similar.— Insequilateral; the reverse. 
{sdquivalves. Equivalve : where one valve is per- 
fectly similar to the other. 
dextrm et sinistrcE. Right and left. If the shell be 
placed upon its base, with the area in front, 
and the valves be then divided, the right 
valve will be opposite the left hand of the 
examiner, and the left valve opposite his 
right hand. 
lacunos(B. Lacunous ; marked with a longitudinal 
depression. 
prominentes . Prominent; when one valve pro- 
trudes in any part beyond the other. 
Umbones. Bosses; the swelling parts near the 
beaks, the highest extreme of which, or 
that point furthest removed from the base, 
we consider as the summit. 
fornicati. Arched ; inwardly much excavated. 
B 
