"I thought this was a brown barnacle until I looked it up and read that they have 4 plates, where these ones have 2. These are also round in shape instead of the ""kite"" shape. Growing next to http://naturewatch.org.nz/observations/2464077 which has a ""kite"" shape. Scotts Point, northern end of the Tohe."
"This is one of the most easy barnacles to recognise by the ""volcano"" shape. It does not grow in large groupings, and is often single, with prominent ridges running up the outside. The base is wider than the top and the plates are inside the walls. The plates are devided down the middle."
Usually found singly or is small groupings, unlike other barnacles that hang out in clusters. This species also can be distinguished by the volcano look.