150 



TWENTIETH REPORT ON THE STATE CABINET. 



The Genus Spirifera is fully represented in the rocks under considera 

 tion. In the Upper Helderberg group, we have : 



Spirifera diiodenaria, 

 S. macra, 



S, raricosta and 



S. grieri, occurring both in the Schoharie grit and in the lime- 



stone above ; which latter likewise contains the following species. 



Spir 



if era gregaria, 



S. 



segment a, 



S. 



oweni, 



S. 



arctisegmenta, 



S. 



acuminata^ 



S. 



eurufeines, 



S, 



macrothyris^ 



S. 



euruteines \2,x.fornaculaj 



S. 



unica (n. s.), 



S. 



maniiii^ 



S. 



disparilis, 



S. 



divaricata^ 



S. 



varicosa, 



S. 



flmbriata. 



S. 



varicosa var., 







The last named species occurs also in the Oriskany sandstone and Scho- 

 harie grit. Several of the species indicated above are known in their perfect 

 condition only in the limestones of this age in Ohio and adjacent States of 

 Indiana and Kentucky. 



In the Hamilton group, the most abundant and widely distributed species 

 is Spirifera mucronata. In the same group are the following : 



Spirifera tullia (n. s.), 



S. 



medialis, 



S, formosa. 



S, 



medialis var. eatoni, 



S, sculptilis, 



S. 



an gust a ^ 



S. ziczac, 



S. 



macronota, 



S. granulifera, 



S. 



subumbona. 



S. marcyiy 







Spirifera acuminata and S.fimbriata recur in this group ; the latter is 

 not uncommon. 



Several species heretofore described are indicated as doubtful, requiring 

 further material and investigation. 



The Portage group has furnished only the Spirifera IcBvis ; which has 

 much the general aspect of a Carboniferous form. 



In the Chemung group, we have : 



Spirifera mesacostalis^ 

 S. mesastrialis, 



S. disjuncta, with its numerous synonyms and the species repre- 



sented in a great variety of aspects ; 

 S, alta (n. s.), • 



iS. prematura (n. s.). 



The chapter on Spirifera is concluded with some remarks upon the 

 geological and geographical distribution of the species of Spirifers, the 

 hinge-structure, etc. ; which have already been published. 



