While the decay-scheme of the even-even isomer ${\mathrm{Os}}^{190m}(10 min)$ has some similarity with that of the "rotational" isomer ${\mathrm{Hf}}^{180m}$, it differs from the latter in that ${\mathrm{Os}}^{190}$ lies in the transition region between the nuclei with rotational and those with near-harmonic level schemes. It was previously believed that the lifetime determining transition in ${\mathrm{Os}}^{190m}$ was a 620-kev transition followed by three lower energy gamma rays. We find, however, that the isomeric transition is a previously overlooked 38.4-kev $M2$ transition with an ${|M|}^{2}=2.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ ("$K$ forbidden"). It is followed by four successive $\ensuremath{\gamma}$ rays. Internal conversion electron studies by means of an intermediate image spectrometer yielded $\ensuremath{\gamma}$-ray energies of 187\ifmmode\pm\else\textpm\fi{}1 kev, 359\ifmmode\pm\else\textpm\fi{}2 kev, 500\ifmmode\pm\else\textpm\fi{}3 kev, and 614\ifmmode\pm\else\textpm\fi{}3 kev. All four transitions are of electric quadrupole character, suggesting that the levels populated are 8+, 6+, 4+, 2+, 0+ (ground state). Delayed coincidence measurements by A. W. Sunyar show that the two lowest energy transitions of 359 and 187 kev take place between the levels 4+\ensuremath{\rightarrow}2+ and 2+\ensuremath{\rightarrow}0+ respectively and it may be expected that also the two higher energy $\ensuremath{\gamma}$ rays follow each other in the order of decreasing energy. However, in contrast to the level spacings in true rotational nuclei, the level energies are far from being proportional to $I(I+1)$, and cannot even be represented with the help of a correction term $\ensuremath{\sim}{I}^{2}{(I+1)}^{2}$.The six-hour osmium isomer, which was discovered by T. C. Chu and assigned by him to ${\mathrm{Os}}^{190m}$, was identified instead as ${\mathrm{Os}}^{189m}$. The half-life was found to be 5.7\ifmmode\pm\else\textpm\fi{}0.1 hour. The isomer decays by a 30.0-kev $M3$ transition to the ground state with ${|M|}^{2}=2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$.