This small pencil urchin is found in various shades of red and white. It has thick primary spines surrounded at the base by a ring of small flattened secondary spines. The primary spines themselves are covered in small spinelets down their entire length, although they are occasionally eroded smooth, or encrusted with epiphytes. Although these spinelets are a giveaway when identifying this species, when they are not visible it can be difficult to distinguish from Goniocidaris impressa. In these cases, the easiest way to differentiate the two species is by the rings of secondary spines, which are flattened in G. tubaria instead of rounded and club-shaped.
