A few stems do not make the regular lengthening of a in the strong cases (except the nom. sing.). Thus:

a. The names of divinities, pūṣán, aryamán: thus, pūṣā́, pūṣáṇam, pūṣṇā́, etc.

b. In the Veda, ukṣán bull (but also ukṣā́ṇam); yóṣan maiden; vṛ́ṣan virile, bull (but vṛ́ṣāṇam and vṛ́ṣāṇas are also met with); tmán, abbreviation of ātmán; and two or three other scattering forms: anarváṇam, jémanā. And in a number of additional instances, the Vedic metre seems to demand a where ā is written.