34 CHARLES D. WALCOTT 



basin is proved by its occurrence on the peninsula of Avalon, to the 

 east of the area of Archean rocks crossing central Newfoundland. 



It is not my intention to discuss the evidence upon which the asser- 

 tion of the presence of these various outlying seas, sounds, etc., is 

 based. The evidence of the existence of such bodies of water has been 

 well presented by Dana.' What I wish to call attention to now is that 

 the Olenellus fauna lived upon the eastern and western sides of the 

 main North American continental area of late Algonkian and early 

 Cambrian time. This view is sustained by the following observations: 

 (i) The strata containing the Olenellus fauna are known only in the 

 eastern and western portions of the continent ; (2) as far as known the 

 Lower Cambrian strata are absent in the interior of the continent ; (3) 

 the Upper Cambrian strata are unconformably superjacent to the 

 Algonkian and Archean rocks over the areas where the Middle and 

 Lower Cambrian formations are absent ; (4) the strata of the Middle 

 and Lower Cambrian are comformably beneath the Upper Cambrian 

 on the eastern and western sides of the present continent in all sections 

 where the three divisions are present. - 



The oldest known portion of the Olenellus fauna is limited to that 

 section of the Cordilleran area mentioned on p. 197. This fauna 

 was undoubtedly present on the continental shelves to the north and 

 south, and may have been distributed around the southern extremity 

 of the central land-area to the Hudson and Champlain valley region. 

 Future investigation may thus prove that the Holmia asaphoides 

 fauna^ of eastern New York is the oldest part of the Olenellus fauna 

 upon the eastern side of the continent, and that it may be compared 

 with the Holmia rowei fauna of the Cordilleran area. The presence 

 in both localities of genera belonging to the Archaeocyathinae indi- 

 cates that warm currents were passing through the straits or sounds 

 to the east and west of the central continental areas, and that condi- 



1 "Areas of Continental Progress in North America, and the Influence of the 

 Conditions of These Areas on the Work Carried Forward within Them." Bull. 

 Geol. Soc. Amer., Vol. I, 1889, pp. 36-48. "Archean Axes of Eastern North America," 

 Am. Jour. Sci., 3d ser.. Vol. XXXIX, 1890, pp. 378-83. 



2 The matter contained in the two preceding paragraphs appeared under the head- 

 ng "Habitat of the Olenellus Fauna" in the Tenth .-innual Report, U. S. Geol. Survey, 

 1891, pp. 556, 557- 



3 Tenth Annual Report, U. S. Geol. Survey- 1891, p. 570. 



