Flora of New Zealand Series

Placodium argillaceum Knight, Trans. Linn. Soc. Lond. ser. 2, Bot., 1: 282 (1878).

Differs from P. parellina in the profuse development of confluent farinose soredia which often cover the whole thallus. It is widely distributed from Auckland to Otago in mainly coastal habitats on rock or soil. Spores are slightly smaller but within the range of variation of P. parellina.