PLATE LXXXIV 



PAGE 



Figs. 1, 2. PLATYCEBAS REFLEXUM Hall 473 



Two views of a specimen in which the aperture is obtusely quad- 

 rangular. Oriskany formation, Ridgely member, Cumberland. 

 (After Hall.) 



Figs. 3, 4. PLATYCERAS ? CALLOSUM Hall 474 



Dorsal and ventral views. Oriskany formation, Ridgely member, 

 Cumberland. (After Hall.) 



Figs. 5, 6. PLATYCERAS SIXUATUM Hall ? 474 



5. Upper view of a small specimen, showing the deep marginal 



sinuosity and the strong wrinkled surface. 



6. Upper view of a larger specimen. 



New Scotland formation, New York. 



Figs. 7, 8. PLATYCERAS TRILOBATUM Hall 475 



Ventral and upper views. [The striae represented between the aper- 

 ture and the next volution do not exist in the specimen.] New 

 Scotland formation, New York. 



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