Covers, things laid out (ppp sterno); ____ viarum (Aen 1.422) the flat beds of the roads (6)

I believe the answer is:

strata

(Other definitions for strata that I've seen before include "Parallel layers" , "bands" , "Layers as of rocks in earth's crust" , "Beds of sedimentary rock" , "Levels, grades or social classes" .)

I've seen this clue in The Times.

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