677 



Plat. 



Platyceras retrorsum, Hall. Pal. N. Y. Vol 3, 1869, p. 320, 



Hall. Fa/. JV.V. Vo/, ///. /STS^. //. SST. ^ 



pl 58, fig. 10a, upper part of spire, shell worn smooth and 

 partly gone; 5, profile showing elevated apex; (?, young, im- 

 perfect. Found in shaley limestone of the Lower Helderherg. 

 VI. ( Among the specimens are some so difi'erent that Hall 

 established as a variety P, abnorme. ) Dr. Barrett has collected 

 it on the Delaware river below Port Jervis, from I. C. White's 

 Stormville shales above and Stormville limestone beneath the 

 Stormville conglomerate of Pike and Monroe counties. G6, 

 pp. 132, 131.— 77. 



Platyceras spinigerum, Worthen, Geo. Sur. 111. Vol. 5, 



i^c. 1873, page 594, plate 28, figs. 



4«, side view of the shell, show- 

 ing the spine bases; ^5, view 

 of the opposite side of the 

 shell ; JfC^ profile view, show- 

 ing the aperture. Distin- 

 guished from all other Coal measure species by groove (sinus) 

 like long depressions and the spines on its surface. Brighton, 

 111., roof shale of Coal No. 6. XIII? 



Platyceras spirale, Hall, Pal. N. Y. Vol. 3, 1859, page 334, 

 plate 63, fig. 4, a young one yet without plications; ba^ 5, a 

 larger one, with some strong plications ; 6, plications partially 

 developed, or only shown by waves of the striae; 7, one smooth 

 in front and plicated a little behind ; 8, larger and strongly 

 plicated; 95, back of another, a little compressed. Found in 

 the slaty beds of the New York Lcuer Helderlerg. VI — In 

 Pennsylvania recognized by Claypole at various outcrops of 

 the Lower HpMerherg chert h^df^^ just under the Oriskany^ in 





