114 TWENTT-SIXTH REPORT ON THE StATE MuSEUIT, 



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

 Helderberg group, near Olarksville, Albany county ; and' at Scho- 

 harie, New York. 



Genus STEIATOPOEA Hall. 



Striatopora Issa n. sjp. 



Coral growing in strong ramose branches, with distant bifurca- 

 tions ; branches three-eighths of an inch or more in diameter. Cells 

 rising from the center of the branch, rapidly increasing in size, and 

 curving outward to the surface ; apertures very unequal, polygonal, 

 strongly striated on the inside, the number of striae increasing with 

 the size of the aperture ; walls not very thick, perforated by large, 

 round pores situated between the striae, and increasing in number 

 with the increase of stri^. The larger cell-apertures somewhat more 

 than a tenth of an inch in diameter. 



This is the most robust species of this genus yet noticed, and the 

 cells are large in proportion. It is not a very common form, and is 

 generally found in detached pieces on the weathered surfaces of 

 blocks of limestone. 



Format^on and locality. — In limestones of the Lower Helder- 

 berg group. 



Genus STREPTELASMA Hall. 



Streptelasma (Petraia) stricta n. sp. 



Cup narrowly turbinate, ver}^ gradually and regularly enlarging 

 at an angle of about thirty degrees, straight or slightly curved 

 except the small apex which is sometimes more abruptly bent. 

 Exterior surface strongly and distinctly ribbed longitudinally, and 

 marked with concentric, unequal undulations of growth : longitudi- 

 nal ribs rounded, from forty-live to fifty-five on specimens, at a point 

 where the diameter is half an inch ; the increase of ribs or rays taking 

 place usually at three distinct points, but sometimes only at two 

 points. Interior of cup broad and deep, with thin sharp margin ; the 

 lamellae not projecting into the cup until near the bottom, but form- 

 ing low, rounded rays, a little stronger than those on the exterior. 



In a slightly flattened specimen which is one inch by three-fourths 

 of an inch in diameter at the margin, with lengtli which has been 

 about one inch and seven-eighths, the number of rays at the margin 

 is fifty-five ; about half of these reach to the center, the other half 

 project only a little beyond the walls at the base of the cup. 



