306 PALEONTOLOGY OF NEW YORK. 



the species is exceedingly abundant and very generally distributed, but it is rarer 

 toward the east where deposits become more arenaceous. Yet wherever the 

 Devonian sandstones are known in Brazil and Bolivia the species abounds. A 

 similar form passing current under the name Sirophomena or Leptcena laticosta, 

 Conrad, also occurs in the lower Devonian sandstones (Coblentzian) of Germany. 

 An additional species, T. occidens, Hall, has been described from the limestones 

 of Hamilton age at Iowa City, Iowa, but its internal characters are not 

 known. 



