Question

geologic time scale. determine the identity of the unknown fossil by using the fossils chart

Explanation:

Step1: Analyze the fossil's time period

The unknown fossil is in limestone. Looking at the geologic time scale, the Ordovician period (490 - 433 million years ago) and Permian period (299 - 250 million years ago) have checkmarks. But the limestone with unknown fossil's associated time - based on the chart's structure and the fossils' time ranges, we match the fossil's appearance (from the limestone tool) to the Ordovician - related fossil (since the Ordovician fossil is in a similar rock - like context here). Also, the other fossils: Cambrian and Silurian have X, Devonian and Carboniferous are empty, Permian has a different - looking fossil (like ammonite - related? No, the shale with ammonite is a tool, but Permian's fossil is different). The Ordovician's fossil in the chart matches the limestone's unknown fossil's context.

Step2: Confirm the identity

By cross - referencing the rock type (limestone) with the geologic time periods and the fossil images, the unknown fossil in limestone corresponds to the Ordovician - period fossil (as the Ordovician box has a checkmark and the fossil in it matches the limestone's unknown fossil's visual context).

Answer:

The unknown fossil (in limestone) is identified as the Ordovician - period fossil (matching the fossil in the Ordovician box on the geologic time scale).