30 NOMENCLAl URE, 



Lunula. Lunule ; a small crescent-shaped de- 

 pression on either the area or areola. 



Margo. Margin j the outline or edge of the 

 shell. 



Radii. Rays. See above. 



eckinati. Spinous ; longitudinally armed with 

 spines. 



vesiculnres. Vesicular ; beset with knots, or pro- 

 minences internally concave. 



Ri.MA. Suture ; the interstice which separates 

 the valves when the ligament is wanting, 

 or the hollow which is covered by the liga- 

 ment. 



clausa. Closed ; the internal lips being thickened 

 so as to cover the whole suture. 



SouAMULiE. Scales. 



canaliculalcB. Channelled; excavated longitu- 

 dinally. 

 Jornicatce. Arched ; concavo-convex. 



imbricalce. Imbricated ; laid partially over one 

 another, like the tiles on a house. 



iubuloscp. Tubulous ; having the sides folded to- 

 gether so as to form a tube. 



