90 
IOWA ACADEMY OF SCIENCE Vop. XXIX, 1922 
PLATE I 
Figs. 1, 4. Cyathodictya oblonga Thomas. 
Fig. 1. A part of the surface of the holotype, x 2kL 
Fig. 4. A view of the holotype, natural size. 
Silurian ; Hopkinton, Iowa. Collected by Samuel Calvin. 
Figs. 2, ‘3, 5. Iowaspongia annulata Thomas. 
Fig. 2. A view of specimen c, x .55, tilted to show the annulations. 
Note the difference between the upper and lower slopes of each ring. 
Fig. 3. Specimen b illustrating the tapering toward the lower end and 
the slight narrowing upward. This individual is somewhat distorted 
and flattened; x about .4. 
Fig. . 5. Specimen a showing the sharp-edged annuli and the concave 
interannular areas. Note the gradual tapering and the progressive 
decrease in width between the rings ; x about .5. 
The three specimens are regarded as cotypes. They were collected 
in the plastic blue shale of the Lime Creek beds at the pit of the 
Rockford Brick and Tile Company, Rockford, Iowa. Specimens a and b 
collected by C. L. Fenton and specimen c by C. H. Belanski. 
