1894.] NATURAL SCIENCES OF PHILADELPHIA. 11 



CRITICAL LIST OF MOLLUSKS COLLECTED IN THE POTOMAC VALLEY. 



BY H. A. PILSBRY. 



The mollusks enumerated in this paper were collected by Mr. 

 .1. E. Ives and the writer during the course of a pedestrian tour 

 through parts of Pennsylvania, Maryland and West Virginia, in 

 September, 1892. The route walked over was as follows: From 

 Gettysburg, Pa., westward to the summit of South Mountain, thence 

 southwest to Maryland, across the Cumberland Valley to Hagers- 

 town, Md. From this point the Cumberland Pike (State road) was 

 followed, with occasional slight deviations, westward to Cumberland, 

 Md. .From Cumberland, Mr. Ives proceeded to Luray, Va., 

 across the multitude ol ranges which traverse West Virginia. The 

 writer returning to Philadelphia, stopping to collect at Cherry Run, 

 on the Potomac River, in West Virginia. 



On such a trip one is constantly tempted to stop by the wayside to 

 examine or collect ; and if he be possessed of that passion for collect- 

 ing "specimens" which is the fatal birthi-ight of most naturalists, 

 these interruptions of the journey are likely to be many and long. 

 The eye soon learns to recognize good collecting-ground; and the 

 mere consideration that supper and a resting-place are miles farther 

 on, is lightly esteemed when the charms and hidden possibilities of a 

 wooded ravine weight the balance. The number of localities repre- 

 sented in this collection is therefore great, as would be expected from 

 the above considerations. Probably almost all of the species of mol- 

 lusks inhabiting Maryland, from the South Mountain to Cumberland, 

 were found l)y us; and as the southern tier of counties in Pennsyl- 

 vania is identical with ^laryland in geologic and topographic features, 

 the list practically tells what that portion of Pennsylvania contains 

 of land and fresh-water shells. The list of a collection made by Mr. 

 Witmer Stone at York Furnace, York Co., Pa., has been kindly 

 furnished by him, and the species occurring there are noted hez-ein. 



The general topography and geology of these portions of Pennsyl- 

 vania and Maryland are well known. South Mountain, the Blue 

 Ridge, Martin's Mountain, Sideling Mountain, Town Ridge, Wills 

 Mountain, and numerous smaller intermediate ridges, cut this district 

 into a series of wide and narrow valleys, trending N. E. by S. W.; 



