We present vibrationally resolved line-narrowed fluorescence spectra of seven centrosymmetric squaraines in polyethylene and polystyrene matrices at 1.4 K. At a fixed excitation frequency, the intensities of the zero-phonon lines decay with lime due to nonphotochemical hole burning,leaving behind a broader background attributed to emission from molecules excited into phonon sidebands. The hole widths are independent of the part of the emission spectrum monitored, suggesting that under these conditions all spectral features arise from a single species or a collection of closely related species. Subtracting the spectra of the hole-burned samples from the initial. spectra leaves predominantly zero-phonon line excited spectra exhibiting enhanced vibrational resolution. A detailed analysis of the vibrationally resolved emission spectra is given, aided by semiempirical AMI force field calculations on the ground electronic state. The dominant Franck-Condon active vibration in all seven squaraines examined is a mode near 150 cm(-1) which is assigned as predominantly an in-plane expansion of the whole molecule but which mixes with other low-frequency motions of the amino group substituents.