482 C. Schuchert — Pre-Canibrian Nomenclature. 



pre-Cambrian rocks tends to show, in the writer's opinion, that 

 there are at least three eras back of the Paleozoic. Therefore 

 we have to consider what they are to be called. The oldest 

 one so far revealed is the Archean, which the writer prefers 

 to know as the Archeozoic. This takes in the oldest known 

 rocks of the Canadian Shield, which are invaded by the Lauren- 

 tian granites as these are now delimited.. Lawson names this 

 time the Ontarian period, or the Ontarian system of rocks. 

 He well knows that his term is preoccupied by the Ontario 

 division of the New York State Geologists, but concludes that 

 the term was "still born". The term, however, has been alive 

 ever since 1842, has always had the value of a period, and js 

 occasionally used even now, a6 Lawson may see if he will look 

 up the references cited below.- 



According to the rules of nomenclature, Lawson's Ontarian 

 must be abandoned; from the writer's standpoint there is no 

 need for it in any event, because the rocks included within it 

 by Lawson represent an era of time and therefore the selection 

 is to be made from Archean or Archeozoic. If, however, a 

 term is needed as a division of Archeozoic time, then Miller 

 and Knight's substitute, Loganian, should be accepted. This 

 term need not be abandoned because of the Logan sill men- 

 tioned by Lawson, nor on account of the Logan sandstone pro- 

 posed in 1869 for a Mississippian formation in Ohio; the latter 

 is a formation name, while Loganian is a different word, has a 

 much larger time value and is, furthermore, based on alto- 

 gether different rocks. 



Until recently the writer thought that Proterozoic was in 

 good standing because of its use in Chamberlin and Salis- 

 bury's Geology. It appears, however, that Agnotozoic has 

 priority, as the following clear definition will show. R. D. 

 Irving in 1887 wrote :t "Some term is necessary to cover all 

 of that great gap which lies between the base of the Cambrian 

 and the summit of the Archean gneissic and schistose base- 

 ment. This name cannot be one of the group rank, since it 



* Ontario division. Vanuxem, Geol. N. Y., Rep. Third Dist., 1842, 13. 

 15. Includes Shawangunk, Medina, Oneida, Clinton, Niagara, but not 

 the highest Silurian. 



— Mather, Ibid., Rep. First Dist., 1843, 2, 353-365. 



— Hall, Ibid., Rep. Fourth Dist., 1843. 18. 



— Emmons, Agriculture N. Y., I. 1846, 141. Includes all Silurian 



formations. 

 Ontarian or Ontario. Clarke and Schuchert, Science, Dee. 15, 1899, 

 875, 876. 



— Weeks, Bull. 191, U. S. Geol. Surv., 1902, 306. 



— Grabau. Science, Feb. 26, 1909, 356. 



— Schuchert, Bull. Geol. Soc. America, xx, 532, 1910. 



— Hartnagel. Handbook 19, N. Y. State Mus., 1912, 44, tables 1, 2. 



— Clarke and Ruedemann, Mem. 14, N. Y. State Mus., 1912, 87. 

 f This Journal, (3) xxxiv, 372-373, 205, 1887. 



