It differs from the underside of G. xenocles by the absence in most specimens of the yellow tornal spot on the hindwing; also the terminal brown margin on the same wing is proportionately much broader and much darker.
This passage describes a specific morphological distinction between two species of insects (G. xenocles) based on their underside anatomy. The key differences are the absence of a yellow spot and the wider, darker brown margin on the hindwing.