98 THE MEDALS OF CREATION. Cuap. VI. 
spokes of a wheel, hence named Actinocyclus (Lign. 7, figs, 
4, 5), and spicules of Sponges, are also abundant. 
When a few grains of the marl are prepared, and mounted 
on a glass, almost all these varieties will be manifest, so | 
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Da 
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Licn. 7. MIcRoOPHYTES* FROM THE RICHMOND-EARTH; highly magnified. 
3 Ag 
Tertiary. Virginia. 
Fig. 1.—Navicuna. la. Side view. 
2.—CoscINODISCUS RADIATUS; a portion of the circular shield. 
3.—GALIONELLA SULCATA; the upper figure shows the transverse 
face of one of the frustules. 
38a. Three united cells viewed laterally. 
4, 5.—ActTinocyctus. Two species. 
6.—COSCINODISCUS PATINA; transverse view. 
6a. Lateral view. 
largely is this earth composed of organic structures ; in fact, 
very few inorganic particles are intermixed, the merest 
* As the term Jnfusorial-earth must be abandoned, it will be con- 
venient to substitute a name simply expressive of the nature of the 
most abundant organisms that enter into the composition of these 
deposits: that of Microphyta, or Microphytes, (from puxpds, mikros, 
small, and gurdv, phyton, a plant), signifying very minute vegetables, 
may perhaps be admissible: in this sense the word microphytal is 
employed in these pages. 
