The area between Ashburton and Newton Abbot, southeast Devonshire, southwestern England, has been mapped in detail with a view to separating the lavas from the intrusive rocks and establishing a stratigraphic sequence. During the lower Devonian, keratophyric tuffs were extruded; the middle and upper Devonian periods were characterized by deposition of limestone and shale and local extrusion of spilitic lavas and vitric tuffs. In the late upper Devonian the volcanism was more widespread, and in upper Carboniferous time consisted of intrusion of sills of spilitic dolerites. The rocks are described and classified petrographically. A comparison is made with the Devonian volcanism in northwest Germany.