For the first time in visible part of the D2 emission spectrum the pseudo doublets representing partly resolved fine structure of rovibronic lines have been observed. They are characterized by splitting values about 0.2 1/cm and relative intensity of the doublet components close to 2.0. It is shown that they are determined by triplet splitting in lower rovibronic levels of various 3Λ±g → c3Π−u electronic transitions. It is proposed to use an existence of such partly resolved fine structure patterns for identification of numerous unassigned spectral lines of the D2 molecule coming from great variety of triplet ”gerade” electronic states to vibro-rotational levels of the c3Π−u state.