GEOLOGICAL SOCIETY OF PENNSYLVANIA. 341 



that although the amount varies considerably in different 

 localities, from fifteen to thirty per cent, yet I believe 

 the discrepancy to have been caused by different depths of 

 water, or peculiarity of situation- — not difference of time 

 in which the species existed. These remarks, how- 

 ever, do not apply to those deposits which are composed 

 almost exclusively of existing species; they are cer- 

 tainly entitled to the appellation of newer pliocene, and 

 occur chiefly in Maryland, North Carolina and South 

 Carolina. 



