BY K. M. JOHNSTON, F.L.S. 



123 



Cuneiform, wedge-shaped ... ... 



Cylindrical, round, like a roller or 

 cylinder. 



Cymbiform, boat-shaped. 



Denticulated, set with small teeth as in 

 Area. 



Dexter valve, right valve. 



Divaricated, spreading out widely. 



Dorsal margin, the side on which the 

 hinge is placed. 



Elliptical, having the form of an ellipse. 



Elongated, lengthened, drawn out. 



Gap, gaping ; when the valves are shut 

 in some bivalves, as in Pholas. an 

 opening is disclosed called the gap. 



Globose, globular. 



Hemispherical, in the shape of a half- 

 globe. 



Inequilateral, when the anterior and 

 posterior sides make different 

 angles with the hinge , Equilateral, 

 having both sides alike. 



Inequivalve when one valve is more 

 convex than the other, or dissimilar 

 in other respects, as in the common 

 oyster. 



Equivalve, having both valves alike. 



Lenticulate, doubly convex, of the form 

 of a lens. 



Ligament, a solid body, softer than a 

 cartilage, but harder than a mem- 

 brane, which connects the valves. 

 External ligament usually attached 

 to ridges on the posterior, hinge- 

 margin behind the umbones. 

 In some bivalves, as in Mactra, the 

 ligament is internal, lodged in a 

 cartilage furrow or pit. 



Dimb, the margin in bivalve shells. 



Eobated, rounded at the edge. 



Eunule, a crescent-like mark or spot, 

 situated near the anterior and 

 posterior slopes. 



Nacred, nacreous, pearly. 



Oblong-ovate, egg-shaped or oval. 



Obsolete, indistinct, not well denned 



Papyraceous, thin as paper. 



Example fig. 

 No. 



(55) 



