292 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
limestones near the base of the Waucoba section), southern Labra- 
dor (reefs 50 feet thick), and to a smaller extent in Nevada, New 
York, Spain, Sardinia, northern Scotland, and arctic Siberia. 
With an abundance of limestone and reef-making animals of world- 
wide distribution in the Lower Cambric, we must conclude that the 
climate at the time was at least warm and fairly uniform in tempera- 
ture the world over. We therefore see the force of a statement made 
to the writer by Walcott some years ago in a letter that ‘‘the 
Lower Cambrian fauna and sediments were those of a relatively 
mild climate uninfluenced by any considerable extent of glacial con- 
ditions,” and also that ‘‘the glacial climate of late Proterozoic time 
had vanished before the appearance of earliest Cambrian time.” 
Toward the close of Lower Cambric time there was considerable 
mountain making, without apparent volcanic activity, going on all 
along eastern North America and to a lesser extent in western Europe. 
These uplifts seemingly had much effect upon the marine life, for 
the Middle Cambric faunas became more and more provincial in 
character in comparison with the earlier, more cosmopolitan faunas 
of Lower Cambric time. 
The Archeocyathine now vanished, and their extinction is sug- 
gestive of cooler waters; there was, however, a greater variety of 
invertebrate forms, more lime-secreting invertebrates, and far more 
widespread limestone deposition in Middle Cambric time. In the 
Upper Cambric the brachiopods, gastropods, cephalopods, and bivalve 
crustaceans were abundantly represented by thick-shelled forms, 
and in most places throughout North America there was marked 
deposition of limestones, magnesian limestones, and dolomites, all 
of which is suggestive of warmer waters. 
Ordovicic and Siluric—The Ordovicic seas from Texas far into the 
arctic regions were dominated by limestone deposits and a great pro- 
fusion of marine life that was also more highly varied than that 
of any earlier time. The same species of graptolites, brachiopods, 
bryozoans, trilobites, and other invertebrate classes had a very wide 
distribution, all of which is evidence that at that time the earth had 
mild and uniform climates. In the Middle Ordovicic and again 
late in that period reef corals were common from Alaska to Oklahoma 
and Texas. | 
Toward the close of the Ordovicic mountain making was again in 
progress throughout eastern North America without significant vol- 
canic activity, but in western Europe, where the movements were less 
marked, volcanoes were more plentiful. The seas were then almost 
completely withdrawn from the continents, and yet when the Siluric 
waters again transgressed the lands we find not only the same great 
profusion and variety of life as before, but as widely extended lime- 
stone deposition. The evidence is again that of mild and uniform 
