Continuing to the northeast, the highway enters Panola County, in which it has junctions with  FM 348,  FM 1971, and  FM 1970 in the community of Clayton. SH 315 then enters Carthage, where it intersects  SH 149.
Proceeding eastward, the highway enters Panola County, where it intersects with FM 348, FM 1971, and FM 1970 in the community of Clayton. SH 315 then enters Carthage, where it meets SH 149.