other WR stars. The excess emission may arise from unresolved circumstellar shells, or within the extended outer envelopes of the stars themselves.

    In a few cases we find clear morphological evidence for WR shells interacting with each other. In several H$\alpha$ images we see WR winds disrupting, or punching through, the walls of limb-brightened shells.
author:
- 'M. A. Bransford, D. A. Thilker, R. A. M. Walterbos, and N. L. King'
title: ' **Shells Surrounding Wolf-Rayet stars in M31**'
---

INTRODUCTION
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Wolf-Rayet (WR) stars are thought to be evolved, massive stars which have lost a significant fraction of their outer envelopes. They are sometimes surrounded by ring nebulae produced via the interaction of the central star with its stellar ejecta or surrounding ambient medium (e.g. Miller & Chu 1993). Studies of the chemistry, morphology and kinematics of Galactic WR ring nebulae have resulted in three main categories (e.g. Chu 1981): (a) radiatively excited regions (R-type); (b) stellar ejecta (E-type); (c) and wind-blown bubbles (W-type). A WR star does not play a primary role in the formation or shape of an R-type shell (generally $>$ 30-40 pc in radius), only in its ionization. An E-type shell is produced when the 