Smithsonian Report, 1948.—Brown PLATE 5 
1. Lengthwise section of an algal pillar with silicified coniferous wood at bottom 
center. Esmeralda formation, 4 miles west of Tonopah, Nev. Natural size. 
2. Cross section of a pillar showing banded chalce -dony center surrounded by 
algal lime. The chaleedony occupies the space vacated by wood. Opal, 
Wyo. X ¥. 
