Maryland Geological Survey 479 



peristome not seen. Most of the specimens show irregular wide grooves 

 o\t"iuli]ig spirally from the ventral side of the aperture half, or more, of 

 the length of the shell. 



This species has some resemblance to P. tortuosum Hall, but is easily 

 separated by its much larger size, more rapid expansion, and by the greater 

 obliquity of the apical portion of the shell. 



Length 4.5 cm. ; diameter of aperture 3.5 cm. 



Occurrence. — Oriskany Formation, Ridgely Member. Cumberland, 

 Maryland ; Knobly Mountain, West Virginia. 



Collection. — Maryland Geological Survey. 



[Oheru.] 

 Platyceras subconicum n. sp. 

 Plate LXXXVI, Figs. 1-3 



Description. — Shell arcuately to obliquely conical ; whorls, one or a little 

 more, free ; shell expanding rapidly at first, then somewhat more gently ; 

 apex blunt, twisted so as to project on the right side of the shell ; aperture 

 subcircular; peristome not observed. Some individuals show a surface 

 marked by faint irregular growth lines. Wide, obsolete, longitudinal 

 ridges are seen on a few shells. The aperture is sometimes irregularly 

 sinuous on the ventral side due to an irregular crinkling of the shell. 



This species was recognized as new by the late Dr. Eowe, and to it he 

 applied the name subconicum. It seems, however, that he did not describe 

 the species ; but the name given by him is here retained. 



Length about 4 cm. ; diameter of aperture 4.3 cm. 



Occurrence. — Oriskany Formation, Ridgely Member. Cumberland, 

 Maryland ; Knobly Mountain, West Virginia. 



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



[Ohern.] 



Platyceras xewberryi Hall 



Plate LXXXVI, Fig. 4 



Platyceras newhcrryi Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 333, pi. Ixiii, 

 figs. 14a-e, 1861. 



Description. — "Shell subdiscoidal, with the last volution expanded: 

 volutions about three, nearly in the same plane; the first two minute and 



