Orth. 



508 



Orthis {Platystwphia) biforata. {Terehratula hiforata^ 



Schlot. Pet. 



1820.) A vari- 

 ety, or young 

 shell. Pal. 

 Ohio, Vol. 1, 



p. 117, pi. 10, fig. 2 a, dorsal view ; 2 J, front view, showing the 

 very prominent mesial fold and deep sinus ; 2 ^, back view ; 2 

 d^ ventral view. Cincinnati {Hudson river) formation^ I I II), 



Orthis {Platystrophia) biforata, Var. acutilirata. {Del- 





r-r 



Sc, 







\ , 





thyris acutilirata. Conrad, Jour. Acad. Nat. Sci. Phila. Vol. 8, 

 1842, Cincinnati group,) Pal. Ohio, Vol. 1, 1873, p. 119, pi. 

 10, figs. 5 a, ventral view of rather large adult; 5, back view, 

 hinge area, incurved beaks ; <?, front ; d^ back of a more trans- 

 verse specimen ; ^, ventral interior, deep scars, hinge area, hole 

 (foramen), hinge teeth, but the comb structure near the teeth 

 does not always occur; /*, back of another specimen; g, mag- 

 nified grained surface, common to all the other varieties of 0, 

 liforata,, where well preserved. — Cincinnati,^ Illh. 



Orthis {Platystrophia) biforata, Var. dentata. {Poram- 



honites 



dentatus,, 



Pander, 



Beit rag. 



Geol. 



Russ. 1830.) Pal. Ohio, Vol. 1, 1873, p. 117, pi. 10, fig. 3 a^ 

 back view of a specimen with two folds in the mesial fold, and 



v**' ' n 



