8 



Sigmoid - s-shaped (see Gyros igma , p. 67) 



Stellate - star-shaped, radiating from a point. 



Striae - linear markings on the frustule which are due to closely placed 

 punctae, or to hollow chambers in the cell wall (may sometimes 

 appear as costae). 



Sulcus - annular groove between the valve mantle and girdle (see Melos ira 

 ambigua , p. 19) 



Uniseriate - having one row of punctae (see Coscinodiscus , p. 31 ) 



Valve - the face of the diatom frustule. 



Valve mantle - the part of the valve which extends below the shoulder. 

 In the Melos iras the valve mantle is a cylindrical surface that 

 may be 30u long (see Melos ira granulata , p. 20) 



Wing - a thin projection of the valve surface, more highly developed than 

 a keel; generally arising near the margin of the valve, but some- 

 times arising near the medial axis. May enclose the "canal" raphe 

 (see Surirella, p. 87) 



