This proposal is to examine and model in detail the formation of a specific class of interacting galaxies known as collisional shell galaxies. It is widely accepted that shell galaxies are formed as a result of an interaction between an elliptical galaxy and a small companion, that could be a gaseous disk galaxy. However, recent neutral hydrogen observations provide evidence that the behavior of the gaseous content of shell galaxies is not what previous models predict, suggesting their formation may not be as simple as it was originally thought. We propose to perform CO observations and extensive numerical modeling of a sample of shell galaxies to specifically study the dynamics of the gaseous content of these systems. The new observations will complement a larger sample of CO observations that have already been collected by the research group of the host institution. With the observations in hand we will construct high resolution models of the dynamics of the systems using a high resolution N-body/gas dynamics code.