Nii has an unusual number of lateral consonants: a typical dental approximant, /l̪/, plus both dental and velar lateral fricatives, /ɬ̪/ and /𝼄/, which are optionally voiced between vowels and do not occur in initial position.[2]
Stucky, Alfred and Dellene Stucky 1973. "Nii phonology", in Alan Healey (ed.), Studies in languages of the Ok family, "Workpapers in Papua New Guinea Languages" 2, pp. 37-78. [1], [2]