PALEOZOIC TIME — UPPER SILURIAN. 573 



In the beds of this region of the Cambrian and Canadian periods there 

 are Salterella rtigosa Billings, closely like the Scottish ; S. Maccullochi 

 Salter ; Kutorgina cingulata B., said by Davidson and Hall to occur in the 

 Lingula flags; Acrotreta gemma B., very near A. subconica Kutorga; four 

 species of Piloceras, a genus described from Scotland, but not known in the 

 United States ; Holometoims Angelini B., very near H. Umbatus Angelin, 

 of Sweden; Nileus macrops B., JV. scrutatus B., iV. affinis B., all closely 

 allied to M armadillo Dalman; Harpides Atlanticus, very near Angelin's 

 H. rugosus of Sweden. In beds of Hudson age there are Ascoceras Cana- 

 dense B., A. Newberryi B., and Glossoceras desideratum B., not found in the 

 United States. In the Upper Silurian there are, as shown by Salter, the 

 British species, Wiynchonella Wilsoni Sow., Orammysia triangulata Salter, 

 G. cingidata His., Platyschisma helicoides Sow., Platyceras Haliotis Sow., 

 Bellerophon expansus Sow., B. carinatus Sow., OrtJioceras bullatum Sow. (?), 

 0. ibex Sow., Homalonotus Knightii Konig, Phacops Downingii Salt. ; to 

 which Billings adds Rhynchonella StricMandi Sow., and Lituites Ameri- 

 canus B., very near, if not quite identical with L. giganteus Sow. Billings, 

 who furnished the above list of species, adds that, through the Cambrian 

 and Canadian periods, there is a decided European tinge in the life, but in 

 the Trenton period its character was peculiarly American. Then in the Hud- 

 son epoch there was again a European tinge, which increased in strength 

 through the Upper Silurian. 



H. M. Ami has given (1892) a list of 163 fossils from the Upper Silurian 

 beds of Arisaig, Nova Scotia, and states that a closer relation exists between 

 the fauna and that of the Ludlow rocks of Kendal in Westmoreland, England, 

 than with either the Silurian rocks of Anticosti, Ontario, or New York. 



EUROPEAN. 



The endogenous growth of the European continent during the Upper 

 Silurian era is manifest, though of less regular progress than that of North 

 America. The Upper Silurian formations over the British Isles were not 

 on the outer Atlantic border, but on the opposite side of a border region 

 of Archaean and Lower Silurian rocks, and this inner side continued to 

 be the region of growth to the end. Moreover, there appear to have been 

 two or three confined and parallel troughs. In Scandinavia and Russia, 

 part of France and the Spanish peninsula, the same is true. All the Upper 

 Silurian rocks of Russia are the work of an Interior Continental Sea, wi'-h- 

 out oceanic aid ; and this great Interior Sea extended south and west over 

 Hungary and Austria to Bohemia and the Alps. The Mediterranean Sea 

 is related to the continent like the West Indies and Mexican Gulf to 

 America. 



The progress through the era was in general quiet ; for the Upper Silu- 

 rian rocks are conformable in superposition. They are horizontal, or very 

 nearly so, over the great interior region in Russia and elsewhere. Nearer the 

 ocean, in England, the rocks to a considerable extent pass regularly upward 



