Lower Helderbero Bryozoa and Corals. 115 



The primary lamellae are smooth on the edge, and strongly granu- 

 lose on the sides below, and sometimes more or less twisted in their 

 direction to the center, although generally direct; uniting and 

 coalescing near the middle, forming an indistinct plate or vesicnlose 

 core, from an eighth to three-sixteenths of an inch in diameter ; and 

 in vertical section, sometimes showing an indistinctly defined vertical 

 wall. 



The secondary lamellf© strongly denticulate on the edge below the 

 surface of the other lamellae. Fosset obscure or obsolete. 



This species is distinguished by the rigid straightness of its form, 

 the strongly ribbed exterior, and the deep wide cup with undeve- 

 loped rays or ribs : and in these characters differs from both those of 

 the Niagara group and also, from those in the higher formations. 



Formation and locality. — In the shaly limestones of the Lower 

 Helderberg group, at Oatskill creek, Greene county ; near Clarks- 

 ville, Albany county; at Schoharie, and at numerous other localities 

 in New York. 



