  The Perseus-Pisces supercluster is known as one of the largest structures in
the nearby Universe that has been charted by the galaxy and galaxy cluster
distributions. For the latter mostly clusters from the Abell catalogue have
been used. Here we take a new approach to a quantitative characterisation of
the Perseus-Pisces supercluster using a statistically complete sample of X-ray
luminous galaxy groups and clusters from our CLASSIX galaxy cluster redshift
survey. We used a friends-of-friends technique to construct the supercluster
membership. We also studied the structure of the Southern Great Wall, which
merges with the Perseus-Pisces supercluster with a slightly increased
friends-of-friends linking length. In this work we discuss the geometric
structure of the superclusters, compare the X-ray luminosity distribution of
the members with that of the surroundings, and provide an estimate of the
supercluster mass. These results establish Perseus-Pisces as the largest
superstructure in the Universe at redshifts z <= 0.03. With the new data this
supercluster extends through the zone of avoidance, which has also been
indicated by some studies of the galaxy distribution by means of HI
observations. We investigated whether the shapes of the member groups and
clusters in X-rays are aligned with the major axis of the supercluster. We find
no evidence for a pronounced alignment, except for the ellipticities of Perseus
and AWM7, which are aligned with the separation vector of the two systems and
weakly with the supercluster.

Cosmology and Nongalactic Astrophysics;Astrophysics of Galaxies