Compressional velocities to 300¿ C and 8 kbar are presented for dry Francisean sandstone, metasandstone, shale, and melange matrix. Mineralogical data, density, and porosity are also given for each rock. Velocity hysteresis was found to vary systematically with experimental temperature and pressure and conditions. This result is tentatively explained on the basis of crack behavior in the rocks. Velocity was found to depend strongly on bulk density and weakly on mineralogy. Samples of shale and melange matrix have velocities similar to sandstone of comparable density. Our results suggest that structural and lithologic complexities in elastic rocks of uniform metamorphic grade will not lead to complex velocity structure. Velocities in rocks of common density are consistent with velocity profiles measured in the upper crust in central California. On the basis of these data the total thickness of Francisean rocks east of the San Andreas fault in central California is 12 km.