The St. Paul Transform System on the equatorial Atlantic is a seismically oceanic transform fault system. This study re-examines the focal depths of 35 earthquakes (M_W 5.3–6.9) from Transforms A, B, and C. The data suggest that the seismogenic zone ranges from 5 to 18 km deep, with the deepest occurring in cooler lithosphere around the center of the transform segments. This challenges earlier hypotheses and indicates a global pattern of cooler mantle in center of oceanic transform faults.