176 NEW YORK STATE MUSEUM 



Genus lichenalia Hall 



[Ety. : XerATjv, lichen] 



(1852. Pal N. Y. 2:171) 



Zoarium a subcircular expansion, consisting of a single lamina^ 

 but often growing in successive layers, the one over the other; 

 zooecia prostrate, elongate subrhomboidal, with a direct, subtubular, 

 outward prolongation or vestibule; apertures rounded, with the 

 peristome much elevated on the posterior side; interspaces de- 

 pressed. 



Lichenalia concentrica Hall (Fig. 79) (1852. Pal. N. Y. 2:171, 

 pi. 37A, fig. 2a, b) 



Distinguishing characters. Circular frond, slightly cup-form in the 

 young state, flattened at maturity; generally variously contorted 

 from irregular growth or accident, and thick at intervals; concen- 





Fig. 79 Lichenalia concentrica 



trically striate and rugose surface, strongest on non-celluliferous 

 side; apertures in concentric lines, narrow, opening on the summit 

 of an elevated pustule. 



Found rarely in the lower Clinton limestone; abundantly in the 

 Clinton lenses; and again rarely in the lower Rochester shale and 

 the Bryozoa bed. Niagara sections. Also at Lockport and else- 

 where (Hall). 



