Calloporina diadema is found from the inner shelf off southeastern Australia. it is frequently found encrusting algal stems or holdfasts. This specimen has not been treated to remove cuticle. As a result, avicularian mandibles, spines and opercula are still present, whereas details of the frontal skeletal wall are obscured.
Original description: Lepralia diadema MacGillivray, 1869
Locality: Williamstown (Victoria)
Type specimen: NMV F45711