Final answer:
The screen that separates the clergy from the congregation in an early Christian basilica is called a templon.
Step-by-step explanation:
The low screen in an early Christian basilica that separates the clergy and sometimes the choir from the congregation is known as a templon. The templon consisted of chancel slabs, colonnettes, and an epistyle or templon beam. This element was part of the architecture of Byzantine churches and evolved over time, allowing laypeople to see into the bema where the altar and clergy were situated. The templon is a precursor to the later developed iconostasis, which is still present in Orthodox churches.