In the first part of the note, we consider a neutrino texture, where the Dirac and righthanded Majorana masses are proportional. If the former are approximately proportional also to the charged-lepton masses, then taking {ITALIC \Delta } m232 \sim 3\times 10-3\mskip \thickmuskip {eV}2 we estimate approximately that {ITALIC \Delta } m221 \sim O(10-5\mskip \thickmuskip {eV}2), what is not very different from the recent KamLAND estimation {ITALIC \Delta } m221 \sim 7\times 10-5\mskip \thickmuskip {eV}2, consistent with the LMA solar solution. In the second part, we show generically that the {ITALIC invariance} of neutrino mixing matrix under the simultaneous discrete transformations \nu e \rightarrow -\nu e , \nu \mu \rightarrow \nu \tau , \nu \tau \rightarrow \nu \mu and \nu 1 \rightarrow -\nu 1 , \nu 2 \rightarrow -\nu 2 , \nu 3 \rightarrow \nu 3 (neutrino ``horizontal conjugation'') {ITALIC characterizes} the familiar bilarge form of mixing matrix, favored phenomenologically at present. Then, in the case of this form, the mass neutrinos \nu 1, \nu 2 , \nu 3 get a new quantum number, {ITALIC covariant} in their mixings (neutrino ``horizontal parity'' equal to -1,-1,1, respectively). Conversely, such a covariance may be the {ITALIC origin} of the bilarge mixing matrix. In Section 5, the ``horizontal parity'' is embedded in a group structure.
PACS numbers: 12.15.Ff, 14.60.Pq, 12.15.Hh
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