The King’s Wattle was described in 1928, it was endemic to Western Australia.
The species was a shrub of about 2 to 3 m height, like most of its kin it did not have leafes as a fuklly-grown plant but so-called phyllodes, leaf-shaped twigs, which in this species were about 0,1 cm long and 0,2 cm wide [which is a odd size in my opinion], and furthermore had yellow flowers.
The King’s Wattle is now most likely extinct.
Two additional wattle species, Acacia mathuataensis A. C. Sm. from Vanua Levu, Fiji and Acacia prismifolia E. Pritz. from Western Australia were formerly thought to be extinct as well, but were both rediscovered in 2015 and 2018 respectively.
The Nullabor Dwarf Bettong was described in 1997 based on subfossil skeletal remains that were found in caves on the Nullabor Plain, an large arid desert region in southern Australia.
The species apparently disappeared shortly after the arrival of European settlers in the region, who brought with them cats and foxes which preyed upon the native mammals and still do so up to this day.
The native people of the Pilbara region allegedly have two names for a very small kangaroo species, weelba respectively wirlpa, which may have originally been used for this species. 
 Chris Johnson: Australia’s Mammal Extinctions: a 50000 year history. Cambridge University Press 2006
The Northern Thick-billed Grasswren was endemic to Western Australia, it was originally discovered near the town of Mount Magnet, it was also found near the town of Wiluna and around Lake Carnegie, where it inhabited the salt-tolerant vegetation.
The Northern Thick-billed Grasswren was not found since 1908 [or 1909 according to which source] and is now extinct.
Western Rufous Bristlebird (Dasyornis broadbenti ssp. litoralis)
The Western Rufous Bristlebird, a slightly smaller subspecies of the Rufous Bristlebird, was discovered in 1901 at a place named Ellensbrook near the Margaret River in Western Australia, it was described as a new species in 1902 based on a single specimen. 
The bird inhabited an extremely restricted range, an about 50 km long stretch of coastal scrub between Cape Naturaliste and Cape Mentelle in the south-western part of Western Australia, where it inhabited dense, stunted shrubland on cliffs and dunes.
The last reliable record took place in 1908, when a second specimen was collected; since then there have been some unconfirmed sightings only and the Western Rufous Bristlebird has finally been listed as extinct in 1999. The reason for its extinction is thought to be the destruction of its shrubland habitat which was repeatedly burnt in the early 20th century to create pasture.
Everything that we know today about the life of this bird comes from the notices of its discoverer.:
“The food of the bird, as revealed by dissection, consisted wholly of land snails, those marine-like looking forms which are found in abundance on the coastal limestone hills, apparently lifeless in hot weather, but full of vitality after a shower of rain. One snail, with the shell perfect, was found in the stomach.” 
 Alex Wm. Milligan: Description of a new Bristle Bird (Sphenura). The Emu 1: 67-69. 1902
Depiction from: ‘John Gould: The Birds of Australia. Supplement. London: printed by Taylor and Francis, Red Lion Court, Fleet Street. published by the author 1869’