  We searched for anomalously long GRBs (GRBs) in the archival records of the
Burst and Transient Sources Experiment (BATSE). Ten obvious superlong (>500 s)
GRBs with almost continuous emission episodes were found. Nine of these events
are known from the BATSE catalog, but five have no duration estimates; we found
one burst for the first time. We also detected events with emission episodes
separated by a long period of silence (up to 1000 s) with a total duration of
1000--2000 s. In the latter case, we cannot reach an unequivocal conclusion
about a common origin of the episodes due to the BATSE poor angular resolution.
However, for most of these pairs, the probability of a coincidence of
independent GRBs is much lower than unity, and the probability that all of
these are coincidences is 10E-8. All of the events have a hardness ratio (the
ratio of the count rates in different energy channels) typical of GRBs, and
their unique duration is unlikely to be related to their high redshifts.
Superlong bursts do not differ in their properties from typical long (>2 s)
GRBs. We estimated the fraction of superlong GRBs (>500 s) among the long GRBs
in the BATSE sample with fluxes up to 0.1 ph cm^{-2} s^{-1} to be between 0.3
and 0.5%, which is higher than the estimate based on the BATSE catalog.
