[2] It has a thallus that is whitish or greyish, often inconspicuous and not always continuous, which can appear darker or dirty grey near its numerous, clustered apothecia.

Sirenophila maccarthyi is distributed across regions including Western Australia, New South Wales, Victoria, Tasmania, and New Zealand, in both coastal and inland habitats.

It typically grows on the bark and dead wood of a wide range of trees and shrubs such as Acacia sophorae, Araucaria excelsa, and various Eucalyptus species.

The lichen was formally described as a new species in 2009 by the lichenologists Sergey Kondratyuk, Ingvar Kärnefelt, and John Elix, who classified it in the genus Caloplaca.

The thalline exciple surrounding the apothecia is zeorine in form and whitish, measuring about 0.04 to 0.05 mm in width and 12 to 20 μm in thickness.

It has been identified on many species, including Acacia sophorae, Araucaria excelsa, Arthrocnemum arbusculum, Atriplex cinerea, Avicennia marina, Bursaria spinosa, Casuarina stricta, several types of Eucalyptus, Leptospermum laevigatum, Leucopogon parviflorus, Lycium ferocissimum, Melaleuca, and Myoporum insulare.

[3] In terms of distribution, Sirenophila maccarthyi inhabits various regions including Western Australia, New South Wales, Victoria, Tasmania, and New Zealand.