  The Deep Survey instrument on the Extreme Ultraviolet Explorer satellite
(EUVE) obtained long, nearly continuous soft X-ray light curves of 5-33 days
duration for 14 Seyfert galaxies and QSOs. We present a uniform reduction of
these data, which account for a total of 231 days of observation. Several of
these light curves are well suited to a search for periodicity or QPOs in the
range of hours to days that might be expected from dynamical processes in the
inner accretion disk around ~10^8 M_sun black holes. Light curves and
periodograms of the three longest observations show features that could be
transient periods: 0.89 days in RX J0437.4-4711, 2.08 days in Ton S180, and 5.8
days in 1H 0419-577. The statistical significance of these signals is estimated
using the method of Timmer & Konig (1995), which carefully takes into account
the red-noise properties of Seyfert light curves. The result is that the
signals in RX J0437.4-4711 and Ton S180 exceed 95% confidence with respect to
red noise, while 1H 0419-577 is only 64% significant. These period values
appear unrelated to the length of the observation, which is similar in the
three cases, but they do scale roughly as the luminosity of the object, which
would be expected in a dynamical scenario if luminosity scales with black hole
mass.
