Comparisons of morphological characters of immature and mature adults of <i>Geotria australis</i> and its synonyms with those recorded in the present study of six lamprey populations (Chubut and Santa Cruz rivers, Argentina; Temuco, Chile; Waikawa and Mokau rivers, New Zealand; Murray River, Australia), three mature <i>G</i>. <i>macrostoma</i> (Santa Cruz River, Argentina) and four mature <i>G</i>. <i>australis</i> (Chillán, Andalién and Maullín rivers and Concepción Bay, Chile).

Comparisons of morphological characters of immature and mature adults of Geotria australis and its synonyms with those recorded in the present study of six lamprey populations (Chubut and Santa Cruz rivers, Argentina; Temuco, Chile; Waikawa and Mokau rivers, New Zealand; Murray River, Australia), three mature G. macrostoma (Santa Cruz River, Argentina) and four mature G. australis (Chillán, Andalién and Maullín rivers and Concepción Bay, Chile).