Reappraisal of an early 20th century excavation at the Cronk yn How round barrow near Ramsey in the Isle of Man suggests that a stone pair was demolished during the 3rd millennium BC to make way for a round barrow with a single central burial. It is suggested that one of the stones from the original pair was decorated with a series of motifs before being incorporated into the barrow. Some of the motifs used find parallels amongst later Neolithic incised rock art on the walls of tombs and houses, and on stone plaques. Other motifs, including what appear to be representations of deer, serve to expand the repertoire of known designs and highlight the potential of this kind of this rather understudied category of rock art. Parallels for the zoomorphic motifs can be found in Scandinavia. A review of other rock art within the Isle of Man revealed more than 70 recorded panels at 55 individual sites making this one of the more densely populated rock art landscapes in the west of Britain. Two main styles are represented, the passage-grave style, which includes the Cronk yn How Stone, and the cup-mark dominated style, or Galician Style. The latter accounts for more than 95% of recorded sites which accords well with what is known of the Isle of Man's cultural relationships during the 4th and 3rd millennia BC.