Annu. Rev. Astron. Astrophys. 1985. 23: 147-168 Copyright © 1985 by Annual Reviews. All rights reserved

Reprinted with kind permission from Annual Reviews, 4139 El Camino Way, Palo Alto, California, USA

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Table of Contents

• INTRODUCTION
• RING GALAXIES
• OUTER RINGS AROUND SPIRALS AND S0s
• POLAR RING GALAXIES
• Observational Properties
• Theoretical Considerations
• Gas Around S0s
• SHELLS AROUND ELLIPTICAL GALAXIES
• Shells, and Ripples
• Theories of Shell Formation
• The Problem of Dust and Gas
• FINAL REMARKS
• REFERENCES