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We examine the relation between stellar mass, velocity dispersion, size,S\'ersic index and $D_n4000$ for ~40,000 quiescent galaxies in the SDSS. At afixed stellar mass, galaxies with higher $D_n4000$ have larger velocitydispersions and smaller sizes. $D_n4000$ is a proxy for stellar population age,thus these trends suggest that older galaxies typically have larger velocitydispersions and smaller sizes. We combine velocity dispersion and size into adynamical mass estimator, $\sigma^2 R$. At a fixed stellar mass, $\sigma^2 R$depends on $D_n4000$. The S\'ersic index is also correlated with $D_n4000$. Thedependence of $\sigma^2 R$ and S\'ersic index on $D_n4000$ suggests thatquiescent galaxies are not structurally homologous systems. We derive anempirical correction for non-homology which is consistent with the analyticalcorrection derived from the virial theorem. After accounting for non-homologousgalactic structure, we measure $M_\ast \propto M_d^{0.998 \pm 0.004}$ where$M_\ast$ is the stellar mass and $M_d$ is the dynamical mass derived from thevelocity dispersion and size; stellar mass is directly proportional todynamical mass. Quiescent galaxies appear to be in approximate virialequilibrium and deviations of the fundamental plane parameters from theexpected virial relation may result from mass-to-light ratio variations,selection effects and the non-homology of quiescent galaxies. We infer theredshift evolution of velocity dispersion and size for galaxies in our sampleassuming purely passive evolution. The inferred evolution is inconsistent withdirect measurements at higher redshifts. Thus quiescent galaxies do notpassively evolve. Quiescent galaxies have properties consistent with standardgalaxy formation in $\Lambda$CDM. They form at different epochs and evolvemodestly increasing their size, velocity dispersion and S\'ersic index afterthey cease star formation.

Velocity Dispersion, Size, S\'ersic Index and $D_n4000$: The Scaling of Stellar Mass with Dynamical Mass for Quiescent Galaxies