Continuous seismic and echo-sounding profiles across the shelf, Florida-Hatteras Slope, and the Blake Plateau reveal the presence of four calcareous ridge systems. The two western-most of these are described in this report; one is buried beneath the Florida-Hatteras Slope, and the other is atop the shelf near the shelf-break. Both ridge systems appear to parallel the slope. The ridge beneath the slope consists of deep-water corals blanketed by as much as 100 m of sediment. The ridge on the shelf is less than 10 m high and was formed in part by calcareous algae. Both ridges are probably of Pleistocene age; the one beneath the slope is early or middle Pleistocene, and the shelf ridge is late Pleistocene.