1894.] NATURAL SCIENCES OF PHILADELPHIA. 29 



A. dilatata Conrad, var. 



North River, at Sedan P. O., Hampshire Co., W. Va., 64,758. 

 A curious elongated form, ecarinate even in the young, and with the 

 basal "spout " almost obsolete. The specimens may perhaps be re- 

 ferable to A. corpuleiita, described from Dan River, N. C. A large 

 series was collected. 



Genus GONIOBASIS Lea. 

 G. virginica Gmel. 



Potomac River at Hancock, Md., 64,778. Canal at Hancock, 

 64,779. Potomac River at Cherry Run, W. Va., 64,780. Also 

 York Furnace, York Co., Pa. (Stone). 



Both smooth and striatetl specimens occur, indiscriminately 

 mingled, as is the case elsewhere wherever I have collected this 

 species. Nearly all of the smooth examples are conspicuously two- 

 banded, as are many of the striated ones also. 



This species is found throughout the larger streams of the Potomac 

 drainage and north to New York and Connecticut, but the soutliern 

 limit of its range has not l)een accurately determined. 



Family VALVATIDJE. 



No specimens were found by us in Maryland. Mr. Stone collected 

 Valvata tricarinatd Say and V. bicarinata Lea at York Furnace, 

 York Co., Pa. 



Family CYRENIDJE. 



Genus SPH^ffiEIUM Scop. 

 S. striatinum Lam. 



The most abundant and commonly distributed species throughout 

 the Middle States. Speciiiiens were taken at Gettysburg, Pa., in 

 Piny Creek, 64,831. Conecochegue River west of Hagerstown, 

 Md., 64,833. Potomac River at Cherry Run, W. Va., 64,829. 

 Warm Spring Creek, Morgan Co., W. Va., 64,832. South Fork 

 of the Shenandoah, west of Luray, Va. , 64,830. 



S. sulcatum Lam. 



Piny Creek, Gettysburg, Pa., 64,842. 



