  We combine all the reliably-measured eigenperiods for hot, short-period ZZ
Ceti stars onto one diagram and show that it has the features expected from
evolutionary and pulsation theory. To make a more detailed comparison with
theory we concentrate on a subset of 16 stars for which rotational splitting or
other evidence gives clues to the spherical harmonic index (l) of the modes.
The suspected l=1 periods in this subset of stars form a pattern of consecutive
radial overtones that allow us to conduct ensemble seismology using published
theoretical model grids. We find that the best-matching models have hydrogen
layer masses most consistent with the canonically thick limit calculated from
nuclear burning. We also find that the evolutionary models with masses and
temperatures from spectroscopic fits cannot correctly reproduce the periods of
the k=1 to 4 mode groups in these stars, and speculate that the mass of the
helium layer in the models is too large.
