Ovolo refers not to the decorative motif appearing on the moulding strip – rather to its general shape. The ovolo shape is wide and convex, ie bulging towards the viewer. If the moulding is concave rather than convex, it is known as cavetto. If it is partly convex and partly concave it is known as cyma. If it is semicircular it is called roll moulding.
Local examples (click to enlarge)
Egg and dart, 2 Castle Street
Egg and dart, Pound Lane