668 HISTORICAL GEOLOGY. 



analogy with the Oriskany in the large number of species of Platyceras, Spirifer, and 

 Strophomenids. (J. M. Clarke, on the Hercynian Question, 42d Rep., Rep. N.Y. State 

 3Ius., 1889.) 



All writers have made the Limuloids of the Middle and Upper part of the era good 

 evidence of equivalency. But there are large species in the Lower Silurian ; and, more- 

 over, they may have lived in brackish or fresh waters, as some facts render probable, so 

 that they really have very little chronological value. 



According to Barrande, the following are characteristic species of his subdivisions, 

 E, r, G, H, of the Upper Silurian of the Bohemian basin : — 



E. Graptolitic slates, passing above into limestone, corresponding to the Niagara 

 period. Many Qraptolites : Halysites catenulatus, Leptcena rhomboidalis, Atrypa (Dayia) 

 navicula, Pentmnerus Knightii, Rhynchotiella, Spirifer., Orthis. Many species of Ortho- 

 ceras, and others of Cyrtoceras, Gomphoceras, Trochoceras, etc. ; Calymene, Phacops, 

 Lichas, Cyphaspis, Illcenus, Cheirurtis, Acidaspis, Proetus. 



F. A dark limestone, cherty above : Favosites Gothlandicus, F.Jibrosus ; Orthis palli- 

 ata, Atrypa reticularis, A. comata, Pentamerus galeatus, Bhynchonella, Spirifer, Leptcena 

 Verneuili ; Phacops, Lichas, Bronteus ; Tentaculites, Goniatites. 



G. A cherty or impure limestone, with an intermediate shaly layer: Atrypa reticu- 

 laris, Pentamerus; Tentaculites ornatus ; Lituites, Goniatites, Orthoceras Midas; Phacops 

 fecunda, Dalmanites Hausmanni, Bronteus, Cheirurus Sternbergi, Proetus, Harpes. 



H. Shale and sandstone : Leptcena, Orthoceras, Lituites, Goniatites, Phacops fecunda^ 

 Proetus, Tentaculites. 



In Russia, on the Baltic, south of the Gulf of Finland, the four subdivisions, G, H, I,. 

 K, have afforded the following species : G. Bhynchonella affinis, Strophomena pecten,. 

 Orthis Davidsoni, Pentamerus borealis, Leperditia Keyserlingi, Phacops elegans. 

 H. Dolomytes and Coral limestone : Syringopora bifurcata, Favosites Gothlandicus, Haly- 

 sites, Pentamerus oblongus. I. The Lower Oesel Zone, dolomytes = Wenlock : Euom- 

 phalus funatus, Orthoceras annulatum, Spirifer crispus, Orthis elegantula, Leptcena 

 transversalis. K. The Upper Oesel Zone, limestones : Pterinea retroflexa, Chonetes 

 striatellus, Spirifer elevatus, Beyrichia tuberculata. 



In New South Wales occur Favosites Gothlandicus, Heliolites inter stinctus, Calymene 

 Blumenbachii, Encrinurus punctatus, Phacops caudata, Atrypa reticularis, Strophomena 

 pecten, Pentamerus Knightii, P. oblongus, Meristella tumida, Orthoceras ibex. 



American Upper Silurian Species Occurring Elsewhere. 



Halysites catenulatus, Niagara, Great Britain (Llandeilo, Wenlock, Aymestry), Norway,. 



Sweden, Russia, Eifel. 

 Heliolites pyriformis, Niagara, Great Britain (Wenlock, Ludlow), France, Sweden, 



Russia, Eifel. 

 Favosites Gothlandicus, Bohemia. 



Eucalyptocrinus decorus, Niagara, Great Britain (Wenlock), Scandinavia. 

 Orthis elegantula, Clinton, Niagara, Great Britain (Wenlock, Ludlow), Gothland. 

 Orthis hybrida, Niagara, Great Britain, Gothland. 

 Orthis biloba, Niagara, Great Britain (Wenlock), Gothland. 

 Plectambonites transversalis, Anticosti, Great Britain (Wenlock), Gothland. 

 Leptcena rhomboidalis, Trenton, through Upper Silurian, into Devonian, Great Britain 



(Wenlock, Ludlow), Sweden, Russia, Belgium, Eifel, France, Spain. 

 Strophomena rugosa, Niagara, Helderberg, Great Britain (Wenlock, Ludlow), Gothland,, 



Russia, Eifel. 

 Spirifer crispus, Niagara, Great Britain (Llandeilo, Wenlock), Gothland. 

 Atrypa reticularis, Clinton, Niagara, Helderberg, Great Britain (Wenlock, Ludlow), 



Gothland, Bohemia, Russia (Urals, Altai) . 



