The affix ṭhak comes in the sense of 'it exists' after the word parimukha being it the Accusative -2nd case in construction.,
Thus परिमुखं वर्तते = पारिमुखिकः 'being before the face,' 'being near or present'.
The word च in the sutra implies that the affix applies to other words also not mentioned. As पारिपार्श्विकः ॥ The word परिमुख is an Avyayibhava compound (II. I. 12). If परि has the force of exclusion 1.4.88, then पारिमुखिकः will mean 'a servant who always avoids the face of his master' \स्वामिनो मुखं वर्जयित्वा सेवको वर्त्तते,\ and if परि means 'all round,' then the word will mean \a servant who is always in the presence of his master -- यतः स्वामिनो मुखं ततस्ततो वर्त्तते\॥,