The other dialect may not need a special term for it, since it is the structurally unmarked, frame-of-reference variety which may be taken as defining that which is normal in the xenolect as well. But were a term to be needed for the non-xenolectal dialect(s), an appropriate one might be matrilect, making up as it does the matrix in which a xenolect is embedded.

These in twelve galleys with vermilion prores Beneath his conduct sought the Phrygian shores..

I’m concerned that she’s becoming an alcoholic.

(historical)