This small, four-plated barnacle gets its common name from its habit of forming tight aggregations, which are often so tightly-packed and eroded that it is hard to determine where one individual ends and the next begins, or even to identify individual plates. This species is similar to Chthamalus antennatus, which can also form tight aggregations. However, while the 6 plates in C. antennatus can usually still be identified, C. tasmanica only has four. In addition, C. tasmanica also has a row of teeth on the outer edge of each of the two smaller moveable (oral) plates.
