C. D. Walcott — Position of the Olenellus Fauna. 385 



Hyolithes. In layers of limestone, still lower in the section, 

 an obscure Strom atoporoid form occurs in abundance.* 



A similar series of rocks occur, unconformably beneath the 

 Cambrian, in Llano County, Texas. Fossils have not been 

 reported from them.f 



The Geographic Distribution of the Olenellus Fauna. 



I have endeavored to show that on the American continent 

 the Olenellus fauna occurs in sediments deposited on the 

 margins of a continental area that, in later Cambrian time, was 

 depressed beneath the sea and largely covered by sediments of 

 Upper Cambrian age4 My studies in Newfoundland, during 

 the past summer, lead me to think that there the Olenellus 

 zone was also a shore deposit about an Archean land area that 

 was probably not depressed deeply, if at all, at any one time, 

 beneath the sea in any part of Cambrian time. 



The Olenellus zone of Norway, Sweden, Russia (Lapland and 

 Esthonia) occurs on the margins of an old Archean continent, 

 and the Olenellus zone of England and probably of Scotland 

 and the Island of Sardinia is on the western side of the Euro- 

 pean area. In other words, the Olenellus fauna, as far as 

 known to-day, lived on the western side of a pre-Cambrian 

 continental area, outlined by the present continent of Europe ; 

 also on the eastern and western sides of a continental area that 

 extended, on the east, from Labrador southwest along the 

 Atlantic coast line, and also on a line now occupied by the 

 valleys of the St. Lawrence, Lake Champlain and the Hudson 

 River, and probably the central line of the Appalachians to 

 Alabama ; and on the west by the eastern ranges of the Rocky 

 Mountains, from Arizona far into British America. 



The correlations in the following table follow the New- 

 foundland section. In New York the Paradoxides zone has 

 not been recognized, unless we consider the representative 

 species, Linnarssonia Taconica, Agnostus desideratus, Agnos- 

 tus, of the type of A. pisifbrmis, Microdiscus connexus, and 

 Zaconthoides Eatoni, as indicating it. This I am at present 

 inclined to do. 



In Newfoundland the genus Olenus is represented, but in 

 New York, Nevada, Wisconsin, etc., the genus Dicellocephalus 

 is taken as the representative genus of the Upper Cambrian. 



In the southern Appalachian area, Tennessee, Alabama, etc., 

 the Upper Cambrian fauna is well developed, and the Middle 

 is indicated by Olenoides Curticei, n. sp., Ptychoparia anti- 

 quata Salter, Agnostus, 2 sp. 



* This Journal, III, vol. xxvi, 1883. pp. 437-442. 

 f This Journal, III, vol. xxviii, 1884, pp. 431-433. 

 % This Journal, III, vol. xxxii, 1886, pp 154-157. 



