PLATE X 



Fig. i. Trigonium arcticum (Brightwell) Cleve; cell in girdle view. 



Fig. 2. Triceratium favus Ehrenberg; cell in girdle view. 



Fig. 3. Triceratium favus Ehrenberg; cell in valve view. 



Fig. 4. Biddulphia striata Karsten ; cells in chain formation, girdle view, 

 showing protoplasmic contents. 



Fig. 5. Biddulphia striata Karsten; cell in valve view. 



Figs. 6, 7. Charcotia bifrons (Castracane) Peragallo. 



Fig. 8. Cocconeis imperatrix Schmidt ; valve view showing pseudoraphe. 



Fig. 9. Cocconeis imperatrix Schmidt ; valve view showing true raphe. 



Fig. 10. Trachyneis aspera (Ehrenberg) Cleve; valve view. 



