सनोतेरनः

The स of the verb सन् , when it loses its न् is changed to ष , under the same circumstances.
Thus गोषाः (Rig. IX. 2.10), formed by the affix विट 3.2.67, the न् is elided by 6.4.41. So also नृषाः ॥

Why do we say 'when it loses its न्'? Observe गोसनिं वाचमुदीरयन् (Atharvaveda III.20.10). Here the affix is इन् 3.2.27. See however गोषणिं in Rig. VI.53.10.

Though this ष change would have taken place by 8.3.106 also, the separate enumeration is for the sake of niyama or restriction. Some however read the word गोसनिः in the list of सवनानि words 8.3.110, and they hold that the proper counter-example is सिसानयिषति ॥ So also सिसनीः formed by adding क्विप् to the Derivative root सिसनिस, thus सिसनिस + क्विप् = सिसनिस् (the अ is elided by 6.4.48) + 0. add सु, सिसनिस् + स् = सिसनिस् + 0 [स् is elided by 6.1.68. Now the final स् (of the Desiderative affix सन्) is liable to be changed either to ष् or to र् (रु). The ष being asiddha, the रु change takes place.] = सिसनिर् = सिसनीः (the lengthening is by 8.2.76). Here the Desiderative affix सन् is not changed to ष, hence this word is not governed by 8.3.61. This being the object of this sutra, there will be ष change in शिषाणयिषति in the Causative.