Marvlaxd Geological Suuvey 477 



Platyceras multisinuatum Hall 



Plate LXXXV, Figs. 4-G 



Platyceras multisinuatum Hall, 1859. Nat. Hist. N. Y., Pal., vol. iii, p. .>19, pi. 

 iviii, figs. 8a, 6, c, and 9a, 6, 1861. 



Description. — "Shell subdiscoid in the yoimg state; apex nearly on a 

 plane with the outer volution : volutions about three, the first ones minute ; 

 outer one becoming free, ventricose, rounded or scarcely angular below, 

 somewhat flattened on the upper side, marked by several ridges and shallow 

 depressions on the upper and dorsal side: aperture somewhat longitudi- 

 nally oval ; peristome sinuate, with a deeper sinuosity on the anterior 

 margin. Surface marked by fine transverse stride, which are strongly un- 

 dulated on the inequalities of the shell, and crossed by fine longitudinal 

 or revolving striae." Hall, 18.59. 



A single individual has been observed which shows as nearly as can be 

 seen, the features in the above description. Although this specimen is 

 fragmentary, the peculiar markings of the species leave no doubt as to the 

 identity of the former. The revolving striae are not observable. 



Occurrence. — Helderberg Formation, New Scotland Member. 

 Cumberland ? 



Collection. — George M. Eoeder. 



[Ohern.] 



Platyceras platystomum Hall ? 

 Plate LXXXV, Fig. 7 



Platyceras platystomum Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 326, pi. 

 Ix, figs, la, b, 2; pi. Ixi, figs, la, &, c, 1861. 



Description. — " Shell obliquely depressed conical, arcuate on the upper 

 part of the first volution; the apex obtuse, consisting of about a single close 

 volution: aperture expanded, campanulate, and sometimes slightly re- 

 flexed. Surface marked by longitudinal plications, which are more or less 

 strongly developed, and are crossed by fine closely arranged lamellose 

 striae, which are often crowded into wrinkles upon the middle and lower 

 part of the shell." Hall, 1859. 



