walcott.J NOMENCLATURE PRIMORDIAL. 243 



In 1844, a separate memoir 1 was published in which a great addition, 

 was made to the Taconic system west of the Petersburg end of the 

 section of 1842. This addition was in 1856 2 separated as the Upper 

 Taconic. 



TACONIAN. 



This name was proposed by Dr. T. S. Hunt, in 1877, to include the 

 Lower Taconic of Dr. Emmons, 3 or the Granular Quartz, Berkshire 

 limestone, and Taconic slates of the latter's typical Taconic section of 

 1842. At the time of the proposal of the name the author was uncer- 

 tain whether the strata included under it should be referred to the basal 

 beds of the Cambrian or to a pre Cambrian system of rocks. 



In a later paper he refers the Tacouian system of the Appalachians 

 to a pre-Cambrian horizon as compared with the Cambrian rocks from 

 that region. This is stated by him as follows : "This Appalachian Cam- 

 brian series is wholly uncrystalline, and is separated from the Tacouian 

 by a stratigraphical break, and by a great interval of time, which in- 

 cludes the Keweenian period." 4 As we now know that the Granular 

 Quartz is characterized by the Lower Cambrian or Olenellus fauna, the 

 Berkshire or Stockbridge limestone by the Chazy-Trenton and perhaps 

 at its base by an Upper Cambrian fauna, and the original Taconic slate 

 of the Lower Taconic of Dr. Emmons is correlated by its stratigraphic 

 position with the Hudson shales, the term Tacouian ceases to be of 

 value in geologic nomenclature. 



PRIMORDIAL. 



This name was used by M. J. Barrande to designate the First fauna, 

 in contradistinction to the Second and Third. 5 



The name was applied at first to the fauna, but, in 1854, in the first 

 edition of "Siluria," Sir Roderick Murchison designated the formation 

 containing the Primordial fauna as the Primordial Silurian, dividing 

 the Silurian into the Upper Silurian, the Lower Silurian, and the 

 Primordial Silurian. The useof the latter term has been advocated more 

 or less by those who oppose the useof the term Cambrian; but the 

 name Primordial is now rarely used except when mentioning the First 

 fauna of Barrande. 



'The Taconic System; based on observations in Now York, Massachusetts, Vermont, and Rhode 

 Island. Albany, 1844, pp. i-vii, 67. 



8 Emmons, Ebenezer. American Geology, containing a full statement of the principles of the 

 science, with full illustrations of the characteristic American fossils. Albany, 1856, vol. 1, pt2, pp. 49-66. 



3 On the geology of the Eozoic rocks of North America. (Abstract). Boston Soc. Nat. Hist., vol. 19 

 1878, p. 278. 



4 Hunt, T. Sterry. The Taconic Question in Geology. Mineral Physiology and Physiography. A 

 second series of chemical and geological essays. With general introduction. 1886, p. 677. 



•Systeme Silurien du centre d© 1* Bohdme, vol. 1, 1852, p. 8§. 



