472 Systematic Paleontology 



This variety is made a spccios by Hall. In the specimens from Mary- 

 land the difference between the typical Platyceras gebhardi and the variety 

 is so slight that it cannot be regarded as of specific value. Indeed, it is 

 extremely doubtful if even a varietal difference exists and the writer is of 

 the opinion that further collections will show the complete identity of 

 Hall's two species. 



Occurrence. — Oriskany Formation, Ridgely Member. Cumberland, 

 east side Nicholas Mountain, Hancock. 



Collection. — Maryland Geological Survey. 



[Ohern.] 



Platyceras magnificum Hall 



Plate LXXXII, Figs. 1-6 



Platyceras magnificii'in Hall, 1859, Nat. Hist. N. Y., Pal., vol. ill, p. 476, pi. 

 cxix, figs. 1-6, 1861. 



Description. — " Shell obliquely subovate. Spire depressed below the 

 plane of the outer volution : volutions two or three, very rapidly expanding 

 and becoming extremely ventricose below, usually free or with the first 

 one contiguous; aperture expanded, subcircular, campanulate, and often 

 with the margin reflexed, particularly on the left side. Surface marked 

 by distinct transverse lamellose undulating strife." Hall, 1859. 



Occurrence. — Oriskany Formation, Riugely Member. Cumberland, 

 east side Nicholas Mountain, Cash Valley, Maryland; Warren Point, 

 Pennsylvania ; Miller's Spring, West Virginia. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



[Ohern.] 



Platyceras subfalcatum n. sp. 

 Plate LXXXII, Figs. 7, 8 ; Plate LXXXIII, Figs. 1-3 

 Description. — Shell subfalcate; whorls (of casts) one; very rapidly ex- 

 panding from beak to aperture, becoming extremely ventricose, and sud- 

 denly contracting at the aperture ; surface marked by low, distant, parallel, 

 longitudinal undulations, sometimes becomes slightly nodulose ; aperture 

 subcircular; outer surface and peristome not seen. Found only as internal 

 casts. 



