EXPLANATION OF THE PLATES. 



PLATE 1. 



Figure 1. Vertical section of Kentucky cannel coal. (X 180.) 



Figure 2. Horizontal section of Kentucky cannel coal. (X 180.) 



Figure 3. Horizontal section of Kentucky boghead coal, showing the 

 supposed colonial Alga, Pila kentuckyana. (X ISO.) 



Figure 4. Horizontal section of another preparation of the same. (X 40.) 



Figure 5. Part of Figure 4 more highly magnified. (X 120.) 



Figure 6. The same showing another part. (X 120.) 



