After an avyayībhāva samāsa the affix ñya is used in the sense of 'who stays there'.,
This debars अण् ॥ The affix ञ्य however, does not come after every Avyayibhava Compound, but only after the words included in the list of परिमुखादि as given in the Ganapatha.
Thus परिमुखं भवं = पारिमुख्यम्, So also पारिहनव्यम् ॥ Not so औपकुलम्, the word उपकुल not belonging to the class परिमुख ॥
1 परिमुख, 2 परिहनु, 3 पर्योष्ठ, 4 पर्युलू, 5 औपमूल, 6 खल, 7 परिसीर, 8 अनुसीर, 9 उपसीर, 10 उपस्थल, 11 उपकलाप, 12 अनुपथ, 13 अनुखड्ग, 14 अनुतिल, 15 अनुशीत, 16 अनुमाष, 17 अनुयव, 18 अनुयुप, 19 अनुवंश, 20 अनुगङ्ग, 21 प्रतिशाख, 22 अनुसाय ॥,