CHAPTER X.

The Upper Silurian period--General succession of the Upper Silurian deposits of Wales--Upper Silurian deposits of North America--Life of the Upper Silurian--Plants--Protozoa--Graptolites--Corals-- Crinoids--General structure of Crinoids--Star-fishes--Annelides-- Crustaceans--Eurypterids--Polyzoa--Brachiopods--Structure of Brachiopods--Bivalves and Univalves--Pteropods--Cephalopods-- Fishes--Silurian literature.