The first was during the Silurian period, just over three hundred million years ago.

The rocks of the area are late middle Silurian period.

These rocks are 414 million years old from the Silurian period.

Thus, the first insects probably appeared earlier, in the Silurian period.

During the Silurian period the state was home to significant reef systems.

Hughes has several different kinds of rock from the Silurian period.

Sea levels rose even further during the ensuing Silurian period.

Local sea levels had dropped by the ensuing Silurian period.

It is the only marrellomorph known from the Silurian period.

By the end of the Silurian period, approximately 420 million years ago, the ocean had disappeared.

The rocks at the site date to the Silurian period of geological time.

The state was submerged by the sea once more during the ensuing Silurian period.

The oldest known scorpions lived around 430 million years ago in the Silurian period.

The geology of the region shows ancient Silurian period formations.

Invasion of land by plants from an aquatic environment occurred late in the Silurian period (441-410 million years ago).

The oldest generally accepted shark scales are from about 420 million years ago, in the Silurian period.

Laurasia was created near the end of the Silurian Period.

Millipedes are some of the oldest known land animals, first appearing in the Silurian period.

This thick sedimentary deposition continued into the Silurian period (444-416 million years old).

The eruption happened about 420 million years ago during the Silurian period, and the volcano has long since become extinct.

They evolved in the sea at the beginning of the Silurian Period, some 50 million years before the first sharks appeared.

Quartizite from the Silurian Period can be found in this water gap.

It preserves fossils dating back to the Silurian period.

Casey is underlaid by rocks from the Silurian period.

The same erosional and depositional processes continued on through the ensuing Silurian period.