Makahoa Pt., Oahu, 13 mm

Ahihi-Kinau NAR, Maui

Rare under Shingle urchins exposed to surf on rocky shores.  It is parasitic, sucking bodily fluid from the host urchin.  The shell is dull, frequently eroded, and fades rapidly.  Attains 0.5 inch, 15 mm.  Known from Hawaii, Cook Islands, and the Tuamotus.  Formerly known as Vexilla lineata.