 The soils east of the Darling Scarp are generally too heavy for this species , with the exception of some isolated pockets of deep alluvial or aeolian yellow sand . B. prionotes thus has a very patchy distribution east of the scarp . This area nonetheless accounts for around half of its geographic range , with the species extending well to the south and south @-@ east of the scarp . In total , the species occurs over a north – south distance of about 815 km ( 500 mi ) , and an east – west distance of about 125 km ( 80 mi ) . 
