The silurian strata are often abundantly fossiliferous.
"Geology"
James Geikie
Here the silurian rocks had broken down, and by the influence of glacier streams and glaciers, now receding, a good deal of rolling, grass-covered land spread from cliff to cliff.
"My Attainment of the Pole"
Frederick A. Cook
So, alternately, at a full second tempo, the four tones rose and fell, carrying out some strange silurian theme: a muffled cadence of undertones, which, thrilled with the mystery of their author and cause, yet merged smoothly with the cosmic orchestra of wind and ripples and distant rain.
"Edge of the Jungle"
William Beebe