Lower Helderberg Fauna. 299 



I have not been able to examine specimens of A. Bistigouchense 

 nor to consult Spencer's description of the species. Fortunately 

 it is figured and discussed by Nicholson (Z. c). For reasons given 

 above it has been removed from the genus Syringosteoma where 

 Nicholson places it. 



ANTHOZOA. 



Family Cyathaxonid^. 



Duncanella, Nicholson, 1874 



Ddncanella rudis, sp. nov. 



Plate II, figures 7, 8. 



Corallum simple, straight, turbinate, rather evenly and rapidly 

 expanding. Rugce on the exterior coarse, and not sharply 

 defined. 



Horizon. — Delthyris Shaly limestone. 



Locality. — The Indian Ladder, Albany county, N. Y. 



This species of Dlncanella is not a rare form in the higher 

 beds of the Shaly limestone of the Helderberg mountains, and 

 specimens of it may have been heretofore identified as Strepte- 

 lasma strictiim. While Streptelasma was attached like most 

 cyathophylloid corals, Duncanella was probably in a free con- 

 dition. The latter also possessed this unique characteristic, that 

 the theca is incomplete at the base, leaving the septa exsert. In 

 Streptelasma, they meet in the center and are twisted to form a 

 pseudo-columella, while this structure is replaced in Ddncanella 

 by a sort of tube reaching nearly to the base, and formed by the 

 extremities of the septa, which do not extend quite to the center. 

 Ddncanella, moreover, is entirely without tabulae or dissepi- 

 mental tissue, which seem to be always present in Streptelasma, 

 although in varying degrees. 



Duncanella rudis differs from D. horealis^ Nicholson, of the 

 Niagara group, in several particulars. It is erect, not bent or 

 uncinate like the latter, while the apical angle is considerably 

 greater. The rugce on the surface are much less numerous and 

 less sharply defined, while the parallel, horizontal growth lines, 

 which are rather characteristic of the Niagara species, are very 

 obscure. 



