PALEOZOIC TIME — LOWER SILURIAN. 



489 



' LOWER SILURIAN ERA. 



Synonymy. — Lower Silurian, Murchison, Phil, Mag., vii. 46, 1835; Brit. Assoc, v., 

 1835. Lower Silurian, Upper Cambrian, Sedgwick, but not aware of their identity, Bi'it. 

 Assoc, Y., 1835. Lower Silurian, including the Lingula flags, Murchison, Sil. Syst., 1838 ; 

 Geikie, in 3d edit, of Jukes's Geol., 1872 ; Dana's Manual of Geol., 1874. Lower Silurian, 

 Lyell, Elements Geol., 2d edit., 1841, and later; Geikie, Text-book Geol., 1885; Seeley 

 and Etheridge, Man. Geol., 1885; Prestwich, Geol., 1886 ; Credner, Geol., 1887. Cambro- 

 Silurian, Jukes, Canadian Geological Survey. Fauna D, or Second Fauna, Barrande. 

 Silurienne, Etage Armoricain, Lapparent, Tr. Geol., 1883. 



Champlain group, but with the Potsdam sandstone and the Oneida conglomerate in- 

 cluded, Hall, Bep. iV. T. G. Surv., 1843 ; same, with the Oneida conglomerate excluded, 

 Mather, Yanuxem, Emmons, Bep. JV. T. G. Surv., 1842, 1843. 



Ordovician, Lapworth (from the name of the British tribe, Ordovices), G. Mag., 1879, 

 p. 13. Upper Cambrian, Ordovician, H. B. Woodward, Geol. of Eng. and Wales, 1887. 



The counter-claims of Sedgwick and Murchison with reference to the 

 geological formations in which they both had worked, appeared to have 

 been settled by the recognition of a Cambrian system below the Lower 

 Silurian. But the independent characteristics of the Lower and Upper 

 Silurian becoming increasingly evident, it has seemed to demand that the 

 two eras should have independent names. Notwithstanding the great 

 claims of Murchison, the new name of Ordovician, proposed in 1879 by 

 Lapworth, is much used for the Loiver Silurian, the one which represents 

 the larger share of Murchison's labors, and thereby the old Murchisonian 

 name of Silurian is left for the Upper division. As this is not the disposal 

 of the question which the law of priority appears to require, the name of 

 Lower Silurian is here retained, awaiting the full expression of geological 

 opinion. 



NORTH AMERICAN. 



2. Trenton 

 Period. 



Subdivisions. 



3. Hudson Epoch : that of the Hudson slate group or 

 Hudson E,iver group, Mather, Ann. Rep. Geol. N. Y., 1840 ; 

 Hudson River group, Mather, Hall, Vanuxem, Final Bep. 

 Geol. iV. y;, 1842, 1843; Lorraine shales, Emmons, Final Rep. 

 N. Y., 1843 ; Nashville group, of Tennessee, J. M. Safford, Am. 

 Jour. Sci., xii., 1851; Cincinnati group, Worthen, Rep. Geol. 

 Ill, i., 1866. 



2. Utica Epoch : that of the Utica slate, N. Y. Geol. Rep., 

 1842, 1843 ; Black slate, Ann. N. Y. Rep. 



1. Trenton Epoch : that of the Trenton, Birdseye, and Black 

 River limestones, Vanuxem, Conrad, Ann. Rep. Geol. N. Y, 

 1838. 



