PREFACE. XI 
Our manuscript was prepared three years ago ;.and its pub- 
lication delayed in order to provide the illustrations. The 
rapid advance of the science, during this brief period, ren- 
dered it necessary that we should re-arrange, and re-write, a 
large portion of it. 
Copious materiel exists toward the remaining OLOGIES of 
the Natural History of Chester County. Who wiil undertake 
the task of making the necessary selections, and giving them 
to the public? 
