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

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

For a PDF version of the article, click here.

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