The self-gravitating spherically symmetric thin shells built of orbiting pa
rticles are studied. Two new features are found. It is the minimal possible
value for the angular momentum of particles, above which elliptic orbits b
ecome possible. And the coexistence of both the wormhole solutions and the
elliptic or hyperbolic orbits for the same values of parameters (but differ
ent initial conditions). Possible applications of this results to astrophys
ics and quantum black holes are briefly discussed.