x PREFACE. 
More recently, the last named gentleman has collected, 
and arranged, an extensive herbarium of AHysterophyta (he 
fungi), a large proportion of which were in the county. 
Thirty years ago, Dr. #. Michener collected, and pre- 
served, specimens of most of the JZammata, Lirds, and Rep- 
tiles, known to inhabit Chester County. More recently, 
Vincent Bernard successfully occupied the same field. ‘These 
important collections have mostiy been placed in the Cabinet 
of Swarthmore College. 
The proverbial richness of our county, in vare and valuable 
minerals, is amply sustained, and illustrated, by the splendid 
Mineralogical Cabinets’ of William W. Jefferis, and other 
Savans. 
Last, but not least; in 1853, Dr. Wiliam D. Hartman 
prepared ‘‘A Descriptive Catalogue of the Terrestrial, and 
Fluviatile, Testaceous Mollusks, of Chester County,’ con- 
taining fifty-nine species. The cost of printing prevented 
the publication at that time of more than ‘‘4 Classified 
’ 
Catalogue’ of the species. 
More than a duplication of the number of species then 
known to inhabit the county, and the progressive improve- 
ments in classification and nomenclature, have rendered 
that Catalogue obsolete, and imperiously calls for one more 
in accordance with the advanced state of the science. Our 
wish, and desire, is to supply this want. And we entertain 
the hope that our effort will be received with indulgence ; 
and, that it may serve to diffuse a taste for, and facilitate the 
study of, this interesting branch of our rich Fauna Cestrica 
among our young naturalists. 
A few extra-limital species have been inserted, from the 
eastern slope of the mountain range, in our State; and which 
may yet occur within this county. 
