90 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



other genera it is perhaps yet to be discovered. Again, Geratiocaris, 

 together with its moveable rostrum, has a bivalved shell, yet habitu- 

 ally keeps its valves half closed, as I learn from perfect specimens. 



Figs. 3-12, a to i. — Geological distribution of Phyllopoda. 



Fig. 3. Hymenocaris, Salter. Lingula-flags or Primordial zone. 



4, 5. Peltocaris, Salter. Lower Silurian (Llandeilo or Caradoc). 



6. Ccratiocaris, M'Coy. Upper Silurian. 



7. Dictyocaris, Salter. Upper Silurian and Lowest Devonian. 



8. Dithyrocaris, Scouler. 1 ^ , .„ 



9. Argas, Scouler. J Carboniferous. 



10, 11. Apus. Trias to Recent. 

 12. Nebalia. Recent. 

 Figs. 3-12 are somewhat reduced ; fig. 7 is less than one-tenth the natural 

 size. 

 a-d. Estheria, Strauss. Natural size. 

 e-i. Leperditia, Beyrichia, &c. Natural size. 



