The straight arc in the galaxy-cluster A bell 2390 is investigated in
the framework of a gravitational lens model that invokes a single back
ground source galaxy. An extended source galaxy at a redshift of 0.913
is being marginally lensed by the foreground X-ray cluster of galaxie
s at a redshift of 0.231. It is demonstrated that a single lensed gala
xy lying on or very near to the lip caustic of the cluster lens is cap
able of reproducing the linear morphology with the observed breaks.