Given a finite volume hyperbolic n-manifold $M$ with totally geodesic boundary, an orthogeodesic of $M$ is a geodesic arc which is perpendicular to the boundary. For each dimension n, we show there is a real valued function $F_n$ such that the volume of any $M$ is the sum of values of $F_n$ on the orthospectrum (length of orthogeodesics). For $n=2$ the function $F_2$ is the Rogers L-function and the summation identities give dilogarithm identities on the Moduli space of surfaces.