The finals of tisṛ and catasṛ are not lengthened before nām (having the augment nuṭ).,
As तिसृणाम्, चतसृणाम् ॥ The very fact of this prohibition proves by implication that the final ऋ of these words is not changed to र before a genitive plural, 7.2.100 notwithstanding. In fact नुट् is added before scope is given to that rule, and thus the preceding rule 7.1.54 prevents the application of the subsequent rule 7.2.100.,