'21'.\ 



Platyceras bucculentum. Hall. ( Fig. P.>7. ) (Pal.N.Y., 

 Vol. V., Pt. II., p. 10, PI. III.) 



Distinguishing Characters.— I rregu lar 

 form; closely inrolled spire, making one 

 or two volutions; rapidly and unequally 

 expanding- lower portion ; rounded longi- 

 tudinal folds or semi-plications; faint re- 



volving striae. 



Fig. 191 Platycercu 

 bueculentum \ a f I e r 

 Ball). 



Found in the Encrinal limestone, at Section 5 (doubt- 



fur 



Hall. (Fig. 198.) (Pal.N.Y., 



and obscure longitudinal 



Fig. 198. Platyceras symmet- 

 ricum. A characteristic specimen 

 — the lower part is too strongly 

 differentiated from the upper i from 

 Hall). 



Platyceras SYMMETRIC !1 m 

 Vol. V., Pt, II., p. 9, PI. III.) 



D is t in g u is h i n g Characters. — 

 Strongly arcuate and incurved 

 form, with one or one and one-half 

 volutions coiled in the same plane, 

 last volution free; equally spread- 

 ing lower portion; oblique, sub- 

 quadrate to rhomboidal aperture; 

 sinuate peristome; concentric 

 striae ; 

 ridges. 



Found in the middle Pleurodictyum bed, in Avery's Creek 

 (rare). 



Platyceras (Orthonychia) attenuatum. Hall. 

 199.) (Pal. N. Y., Vol. V., Pt. II., p. 6, 

 PI. III.) 



Dist in g u is h in g Characters. — Conical 

 form ; minute and slightly inrolled apex, 

 making from one to one and one-half volu- 

 tions; abrupt expansion of body-whorl; 

 very oblique peristome ; crowded, undulat- FlG 199 piatycenu 



ing concentric striae; irregular, undefined SaiiT'" "''"'' 



longitudinal folds ; sinuous peristome. 



Found in the Encrinal limestone, and the Stictopora and 

 Demissa beds, at Section 5; in the Trilobite beds, at Section 

 8 (rare). 



( Fig. 



