GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 



145 



Strophonella headleyana [fig. 43], Leptostro- 

 p h i a b e c k i [fig. 44] and Orthotlietes w oolwor th- 

 an u s [fig. 45] are the most characteristic strophomenoid shells. 

 Of these the first two are characterized by a crenulated hinge 

 line, the first having the convexit}^ of the valves reversed while 

 L. becki is normal, often almost flat, and not infrequently 

 with concentric wrinkles; the spreading muscular impressions 

 are also very characteristic. O. woolworthanus likewise 

 has the convexity of the valves reversed, but has a broader hinge 

 area than S. headleyana and no crenulations. 



Fig-. 50 ITncinulvis abruptus 



L e p t a e n a r h o m b o i d a 1 i s [fig, 46] one of the common- 

 est brachiopods of this horizon, is easily recognized by the strong 

 concentric wrinkles and the abrupt anterior deflection. 



Among the Spirifers S . p e r 1 a m e 1 1 o s u s [fig. 47] is readily 

 recognized by its rounded plications and strong lamellose con- 

 centric striae; while S. macropleura [fig. 48], the most 

 characteristic species of this horizon, may be known by its large 

 size, few, very broad and gently rounded plications and numerous 

 fine radiating striae. 



Among the rhynchonelloid shells Uncinulus nu.cleo- 

 latus [fig. 49] U . abruptus [fig. 50] and U. velli- 

 c a t u s [fig. 51] occur, all of which are robust and readily dis- 

 tinguished by the characters shown in the illustrations. 



