The Forest Pamakani is a rather tall, upright growing shrub that may reach hegths of up to 2 m. 
The nominate race of the species is thought to have been found on the island of Kaua’i, the northernmost island of the Hawaiian main island chain, this taxon, however, is known exclusively from a single collection and the exact locality has never been recorded.
The only other subspecies (Tetramolopium consanguineum ssp. leptophyllum (Sherff) Lowrey) is endemic to the island of Hawai’i, the species does not occur on any of the islands between Hawai’i and Kaua’i, making the record from Kaua’i very questionable.
The nominate race was never recorded since the type collection and is now considered extinct. 
 Timothy K. Lowrey: A biosystematic revision of Hawaiian Tetramolopium (Compositae: Astereae). Allertonia 4: 325-339. 1986
The Sand Pamakani occurs on the islands of Hawai’i and Maui, Hawaiian Islands, with the nominate race occuring on both islands and the subspecies, discussed here having been restricted to Maui only.
The Loose Sand Pamakani is considered extinct, the same was thought of the nominate race, which, however, was rediscovered in 1989. 
 Timothy K. Lowrey: A biosystematic revision of Hawaiian Tetramolopium (Compositae: Astereae). Allertonia 4: 325-339. 1986  Patricia P. Douglas; Robert B. Shaw: Rediscovery of Tetramolopium arenarium Subsp. arenarium var. arenarium (Asteraceae: Astereae) on the Pohakuloa Training Area, Hawaii. Annals of the Missouri Botanical Garden 76(4): 1182-1185. 1989