890 PALJJONTOLOGY OF NEW-YORK. 



Platyceras pIat}stohiuiii ( n. b.)- 



Plate LX. Fig. I a b, & 2 ; and Plate LXI. Fio. 1 a, b, c. 

 Shsu. 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 reflexed. 

 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. 



This species bears some resemblance to P. perplicatum ( Plate lix, fig. 8), but is 

 more obtuse at the apex and more ventricose below. 



PLATE LX. 



Fig. 1 a. View of the right side of a specimen, the apex of whibh is broken off. 



Fig. 1 b. The cast of a similar specimen, preserving the impressions of the plications. 



Fig. 2. A similar specimen, showing a little irregularity at the apex. The plications are~ 

 shown only on one side. 



PLATE LXL 

 Fig. 1 a. The left posterior side of a specimen, which is crushed on the upper side. 

 Fig. 1 6. The anterior side of the same, the distortion being due to pressure. 

 Fig. 1 e. A young individual which is somewhat distorted by pressure. 

 Geological position and locality. In the central part of the Lower Helderberg 

 group : Albany and Schoharie counties. 



Plat^'ceras platystoinnin, var. alyeatuiii. 



Plate LX. Fio. 3 a, 6, c. 



Sbbll somewhat hemispheric : apex posterior, abruptly incurved, con- 

 sisting of a single volution ; body volution abruptly spreading, very 

 ventricose : aperture circular ; peristome sinuate on the posterior side, 

 and entire on the anterior side. 



Surface plicate on the posterior and left sides, the right side showing 

 some longitudinal pustules ; the whole marked by fine closely arranged 

 transverse striae, which are somewhat wrinkled on certain parts of the 



shell. 



Fig. 3 a. The right side, showing the upper side of the spire. 

 Fig. 3 6. The left posterior side. Fig. 3 c. View of the aperture. 



Geological position and locality. In the middle part of the Lower Helderberg 

 group : Schoharie county. 



