was collected in 1902 by J. T. Tunney; he had killed this animal at Nellie Creek. P. concinna monastria (Thomas, 1926) A subspecies restricted to the Kimberley region. Description A species of Petrogale, the rock wallabies, distinguished by its small size. The pelage is a grey colour, with reddish highlights at the fore-arm, legs and hind parts. The tail is also reddish grey, with a bushy end of coarser hair that begins two thirds along its length, the total length may be from 260 to 335 millimetres. The cheek is marked with a whitish stripe from the eye to the nostrils, a lighter tone that contrasts with the blackish parts of the snout. Another darker stripe is found below the eye and down the neck, the region beneath the fore-arm is also blackish. The head and body length combined in 310 to 365 mm, the smallest of the genus but for P. burbidgei. The measurement of the hindfoot is 95 to 105 mm, the ear from base to tip is 41 to 45 mm. The weight range is from 1.2 to 1.6 kilograms. The dentition of P. cocinna is unique amongst the marsupial species, with the supernumerary molars being continually replaced. These teeth emerge in a regular size and shape, with each row containing four to six molars and another that is yet to erupt. The early loss of the premolar appears to allow this regeneration to continue throughout their life. Nabarlek is often found with the similar P. brachyotis, whose coloration is more variable, and a young individual may be indistinguishable from this species in field observations. Behaviour Nabarlek move quickly with a distinctive horizontal posture, the tail curled toward the middle of the back with raised hairs in the tufty end. The species has a timid disposition, although is somewhat gregarious in associations with others. Their feeding and other activities is usually nocturnal, and they may range beyond their refuge to forage. The species will range several hundred metres from its secure position, foraging in the surrounding black soil terrain, this contrasts with the less venturous behaviour of the short-eared P. brachyotis. The discrete and cautious nature of narbarlek makes capture of specimens difficult, they are regarded as 'trap-shy' in attempts to survey their population. Diet The diet includes a variety of plants, including grasses, ferns and sedges. The plants consumed in Arnhem land during the wet season