Distinguishing characters of Hemigenia rigida, a conservation significant species confused with H. pritzelii (Lamiaceae: Westringieae)

Hemigenia rigida Benth. (sect. Homalochilus Benth.) is a species of high conservation concern from Western Australia’s Avon Wheatbelt known from three collections made 150 and 20 years apart. Hemigenia pritzelii S.Moore (also sect. Homalochilus), a more frequent species from the Jarrah Forest of south-west Western Australia, has been frequently confused with H. rigida and both were previously confused with H. ramosissima Benth. The mis-application of the name H. rigida to the distinct and more abundant species H. pritzelii has hampered recognition of the potentially dire conservation status of H. rigida. To resolve longstanding confusion, distinguishing characters are provided for H. pritzelii and H. rigida along with morphological descriptions, distribution maps and information on ecology. An interim key to the species of sect. Homalochilus is presented for context and to aid identification.