After the word prāvṛṭ being in the Locative -7th case-affix, there is the affix ṭhap in the sense of 'produced therein'.,
This debars एण्य of sutra 4.3.17. The प् of ठप् is for the sake of accent. प्रावृषि जातः = प्रावृषिकः 'produced in the rainy season'.,