PLATE VII 



Fig. i. Corethron criophilum Castracane; " hystrix" phase, cell in girdle 

 view showing protoplasmic contents, and the imbricate scale-like 

 markings on the connective zone. 



Fig. 2. Corethron criophilum Castracane ; valve view. 



Fig. 3. Corethron criophilum Castracane; small daughter cell within 

 parent girdle. 



Figs. 4, 5. Corethron criophilum Castracane; auxospores. 



Figs. 6, 7, 8, 9, io. Corethron criophilum Castracane; cell ends, showing 

 variation in convexity. 



