EVOLUTION OF EARLY PALEOZOIC FAUNAS 199 
American continent of today. Strictly speaking the fauna did not live 
upon the outer shore facing the ocean, but on the shores of interior 
seas, sounds, straits, or lagoons that occupied the intervals between 
the several land-masses that rose from the partly submerged conti- 
nental platform east and west of the central continental area. On the 
eastern side, the first land east of the central portion of the continent 
extended from Alabama northeast along the line of the present Appa- 
lachian range to and including the Green Mountains of Vermont. 
Whether or not the fauna existed in the Connecticut River region to 
the east of the Green Mountains is unknown. That it occurred 
further east is shown by its presence in eastern Massachusetts and 
northwestern Newfoundland. Its presence in a still more easterly 
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: 
(1) 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 
« “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. 1, 1889, pp. 36-48. ‘‘ Archean Axes of Eastern North America,” 
Am. Jour. Sci., 34 ser., Vol. XX XIX, 1890, pp. 378-83. 
2 The matter contained in the two preceding paragraphs appeared under the head- 
ing ‘Habitat of the Olenellus Fauna” in the Tenth Annual Report, U. S. Geol. Survey, 
1891, pp. 556, 557- 
