AMERICAN EQUIVALENTS 249 



in some higher member of the Lower Helderberg.* These figures show 

 that the Tentaculite limestone is transitional to the Lower Helderberg, 

 yet its fauna does not forcibly bring to mind that of the Lower Pen- 

 tamerus immediately above. 



Fauna of the Tentaculite Limestone of Neiv York 



f Homocrinus scoparius Hall. 



Monotrypa (?) spinulosa (Hall and Simpson), 

 f StropJieodonta varistriata (Conrad). 

 -- X Orthothetes hydraulicus (Whitfield). 27859. \ 



Spirifer vanuxemi Hall. 4692, 9112, 26043, 10549. 



TeUinomya nucleiformis Hall. 



Goniophora dubia (Hall). 4693. 



lllionia sinuata (Hall). 



Aviculopecten (?) obscura (Hall). 



Holopea subconica Hall. 



Holopea antiqua (Vanuxem). 10625. 



Holopea pervetusta (Conrad). 

 ?f Holopea (?) elongata Hall. 



Murchisonia extenuata Hall. 



Murchisonia minuta Hall. 

 ? f Euomphalus sinuaius Hall. 



Tentaculites gyracanthus (Eaton). 5001, 10549, 17514, 9120. 

 f iSpirorbis laxus Hall. 



Oncoceras ovoides Hall. 



Cyrtoceras subrectum Hall. 10628, 4682. 



Leperditia alia (Conrad). 4699, 9115, 17515, 25853. 



Leperditia parvvla Hall. 10551, 10552. 



Beyrichia parasitica (Hall). 



Beyrichia clarkii Jones. 



Beyrichia trisulcata Hall. 

 \Klcedenia notata (Hall). 10551, 10552. 



American paleontologists acquainted with this fauna and that of the 

 typical Lower Helderberg will at once see that it is not the Tentaculite 

 fauna which gave the Lower Helderberg sea its multitudinous forms 



* In Ohio a similar fauna is present in the " Hydraulic limestone of the Lower Helderberg " (Geol . 

 Survey of Ohio, vol. vii, 1893, pp. 410-418). The following are the species : 



Orthothetes hydraulicus (Whitfield). Pentamerus pesovis Whitfield. 



Spirifer vanuxemi Hall. * Pterinea aviculoidea Hall. 



* Meristella Icevis (Vanuxem). Goniophora dubia Hall. 



* Meristella bella Hall. Eurypterus eriensis Whitfield. 

 Nucleospira rotundata Whitfield. Leperditia alta Conrad. 



* RhyncJiospira f,ormosa Hall. Leperditia angtdifera Whitfield. 

 Ehynchonella hydraulica Whitfield. 



t Also in higher Lower Helderberg. 



t Also in the Onondaga (= Cayugan). 



§ Register number of the specimens in the U. S. National Museum. 



XXXVII— Bull. Geol. Soc. Am., Vol. 11, 1899 



