Makylaxd Geological Survey GS;j 



Genus PLATYCERAS Conrad 

 i'LATYCERAS MARYLANDICUM 11. Sp. 



Plate LXX, Figs. 12-16 



Dcscripiion. — Shell subconieal, arcuate. Apex minute, slightly cuiaciI 

 and twisted. Body volution expanding rapidly near apex, less ra])iilly 

 toMard aperture in larger shells. Young specimens are slightly, uhler 

 specimens more strongly curved, the anterior convex side becoming 

 nearly twice as long as the posterior concave side. Right and left sides 

 subequally convex. Aperture oblique. Surface marked Ijy a few irregu- 

 lar longitudinal folds which are obsolete toward apex, but become dis- 

 tinct in some individuals or even pronounced near aperture. Casts of 

 some shells slightly nodose. 



Length of convex side 50 mm. in large specimens; diameter aper- 

 ture 30 mm. 



This species resembles P. conicum Hall of the Onondaga and Hamil- 

 ton of Xew York but is more arcuate. It is distinguished from the other 

 species of the fauna by its larger size and large apical angle, while the apex 

 is not attenuate. 



Occurrence. — Jennings Formation, Chemung Me,mber. Williams 

 Eoad, on Polish Mountain, 2012. Parkhead Member. Williams Eoad, 

 on Polish Mountain, 1600 common; 2 miles west of Pawpaw 1763 ?; 

 Millstone, 1772 ?. 



CoIIccUon. — Maryland Geological Survey. 



Platyceras compkessum n. sp. 

 Plate LXX, Figs. 1-3 



Description. — Shell subconieal, arcuate. Shell strongly compressed, 

 the transverse diameter being about one-third the dorso-ventral diameter. 

 A2>ex incurved; body volution expanding rapidly from a point near apex. 

 Dorsal margin subangular, curved, forming a semicircle; ventral margin 

 short, concave. Eight side convex, left side concave. Aperture elliptical, 

 its edo'es curved. Surface ornamented bv growth lines which curve 



