Faunal Stages were very important in the 19th and early 20th Century as they were the major tool available for dating rock beds until the development of seismology and radioactive dating in the second half of the 20th Century.
Faunal stages are regional. They often include many formations of differing rock types that were being laid down in different environments at the same time. In recent years, regional and global correlations of rock sequences have become relatively certain and there is less need for faunal labels to refine the age of formations. There has been a tendency to use European and, to a lesser extent, Asian, stage names for the same time period world wide even though the faunas in other regions may have little in common with the stage as originally defined.
A summary of most commonly used marine faunal stage names can be found at http://flatpebble.nceas.ucsb.edu/public/harland.html