The affix ḍmatup comes after the words 1. kumuda 2. naḍa and 3. vetasa in the above four senses and the final of these words is elided before this affix.,
Thus कुमुद्वान्, नड्वान्, वेतस्वान् ॥
Vart:- So also after the word महिष, as महिष्मान् ॥,
कुमुद-नड-वेतसेभ्यो ड्मतुप्
Adhyāya 4 · Pāda 2 · Rule 87