262 PALAEOZOIC TIME — UPPER SILURIAN. 



Atrypa reticularis, Great Britain (Wenlock), Sweden, Russia (Urals, Altai), 



Bohemia. 

 Dalmania nasuta, Great Britain, Sweden, Russia. 



Eurypterus remipes, Russia (island of Oesel, according to Keyserling). 

 Pentameru8 galeatus, Great Britain (Aymestry, Dudley, Ludlow), Eifel. 



There are a number of other species closely like European, but they are 

 regarded by Hall as distinct. 



&. Arctic American Upper Silurian Species occurring elsewhere. 



Halysites catenulata, Great Britain, Norway, Sweden, Russia, U.S. 



Favosites Gothlandica, Great Britain, Sweden, U.S. 



Favosites polymorpha, Great Britain, France, Belgium, Eifel. 



Stromatopora coneentrica, Great Britain, Eifel. 



Beceptaculites Neptuni De Prance, Great Britain, Belgium, Eifel, U.S. 



Orihis elegantula, Great Britain, Gothland, Russia, U.S. 



Atrypa reticularis, Great Britain, Gothland, Urals, Altai in Siberia, U.S. 



Pentamerus Gonchidium Dalman, Gothland. 



Rhynchonella sublepida ? De Verneuil, Urals. 



Encrinurus levis f Angelin, Gothland. 



Leperditia Baltica Hisinger, Gothland. 



There are a considerable number of species in the British Lower Silurian 

 which pass into the Upper Silurian. They are found mingled in the inter- 

 mediate Llandovery formations, which, although classed with the Upper Silurian, 

 contain between 40 and 50 species that occur also below. 



Barrande has found nearly 2000 species of fossils in the Bohemian Silurian 

 basin above the Primordial strata. The limestone E abounds in organic re- 

 mains, and among them are 400 species of Cephalopods, and 78 species of TrL 

 lobites (of the genera Calymene, Acidaspis, Cheirurus, Cyphaspis, Lichas,Phacops, 

 Harpes, Bronteus, and Proetus). Barrande regards this as the culminating period 

 for the Trilobite race. Limestone F also contains 75 species of Trilobites, and of 

 the same genera, associated with a profusion of Brachiopods. In G there are 

 many Goniatites and other species, which show that, while the strata are inti- 

 mately connected with E and F physically and. in their fossils, the period 

 probably corresponds in part with the early Devonian. Besides 40 species 

 of Trilobites of the above genera, there are others of the Devonian genus 

 Dalmania. In Bohemia 57 Lower Silurian species pass into the Upper 

 Silurian. 



A list of the genera common to the American and European 

 continents would show almost a complete identity, and the same 

 system of progress from the Lower Silurian onward. In each, the 

 genera Spirifer and Chonetes, among the Brachiopods, were added to 

 Orthis, Leptcena, and Atrypa; Halysites (Chain-corals), Favosites, and 

 Cyathophyllidce became abundant ; Crinoids were greatly multiplied ; 

 and the Eurypterus group or Cyclopoid Crustaceans commenced a 



