  Experiments and simulations have been performed to examine the
finite-temperature behavior of Ga$_{17}{}^{+}$ and Ga$_{20}{}^{+}$ clusters.
Specific heats and average collision cross sections have been measured as a
function of temperature, and the results compared to simulations performed
using first principles Density--Functional Molecular--Dynamics. The
experimental results show that while Ga$_{17}{}^{+}$ apparently undergoes a
solid--liquid transition without a significant peak in the specific--heat,
Ga$_{20}{}^{+}$ melts with a relatively sharp peak. Our analysis of the
computational results indicate a strong correlation between the ground--state
geometry and the finite--temperature behavior of the cluster. If the
ground--state geometry is symmetric and "ordered" the cluster is found to have
a distinct peak in the specific--heat. However, if the ground--state geometry
is amorphous or "disordered" the cluster melts without a peak in the
specific--heat.
