46 NOMENCJ.ATURE. 



Lunula. Lunule ; a small crescent-shaped de- 

 pression on either the area or areola. 



Margo. Margin, the outline or edge of the 

 shell. 



Radii. Ra\s. See above. 



eclwiati. Spinous ; longitudinally armed with 

 spines. 



vesicular es. Vesicular ; beset with knots, or pro- 

 minences internally concave. 



RiMA. Suture; the interstice which separates 

 tlie valves when the ligament is wanting, 

 or the hollow which is covered by the li- 

 gament. 



clausa. Closed; the internal lips being thick- 

 ened so as to cover the whole suture. 



Squamul^. Scales. 



canaliculatcB. Channelled ; excavated longitu- 

 dinally. 



fornicatce. Arched; concavo-convex. 



imhricatce. Imbricated; laid partially over one 

 another, like the tiles on a house. 



tubulosce, Tubulous ; having the sides folded to- 

 gether so as to form a tube. 



