  Suppose $G$ is a second countable, locally compact, Hausdorff groupoid with a
fixed left Haar system. Let $\go/G$ denote the orbit space of $G$ and $\cs(G)$
denote the groupoid $C^*$-algebra. Suppose that $G$ is a principal groupoid. We
show that $C^*(G)$ is CCR if and only if $\go/G$ is a $T_1$ topological space,
and that $C^*(G)$ is GCR if and only if $\go/G$ is a $T_0$ topological space.
We also show that $C^*(G)$ is a Fell Algebra if and only if $G$ is a Cartan
groupoid.
