A CONTRIBUTIO^T TO THE LoWER DEVONIAN FAUNAS OF MARYLAND 37 



Plattceras gracile n. sp. 

 Plate LXXXA^ Figs. 10-13 



Description. — Shell spirally and obliquely ascending; whorls one or 

 one and one-half; shell gracefully and spirally tapering regularly to an 

 acute apex, the summit of which lies about in the plane of the right side 

 of the aperture ; surface marked by irregular growth lines which often tend 

 toward irregular, low undulations; aperture slightly higher than wide; 

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

 extending spirally from the ventral side of the aperture half, or more, of 

 the length of the shell. 



This species has some resemblance to P. tortuosiim 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. 



Occurreyice. — Oriskany Formation, Kidgely Member. Cumberland, 

 Maryland; Knobly Mountain, West Virginia. 



Collection. — Maryland Geological Survey. 



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, longi- 

 tudinal ridges are seen on a few shells. The aperture is sometimes irregu- 

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



This species was recognized as new by the late Dr. Rowe, 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. — Marvland Geological Survev, U. S. National ]\luseum. 



