The Diadematacia are a superorder of sea urchins. Unlike most other sea urchins, they generally have hollow spines. The tubercles on their tests are perforated, and most species possess gills.
References
Book: Barnes, Robert D. . 1982 . Invertebrate Zoology . Holt-Saunders International . Philadelphia, PA. 980. 0-03-056747-5.
