For div is also substituted divas (as well as a dyāvā) when pṛthivī follows in a dvanda samāsa of names of devatā-s.,
Thus दिवस्पृथिव्यौ, द्यावापृथिव्यौ ॥ The word दिवस् is exhibited in the aphorism as दिवस् ending in अ, in order to indicate that the स् of दिवस् is not changed to ह् or a visarga or upadhmaniya when followed by पृथिवी ॥ Following is an anomalous use there being no Dvandva compounding here. द्यावा चिदस्मै पृथिवी ममेते ॥,