This first study of the major contributions by Sarah née Wallis, Mrs T(homas) Edward Bowdich, then Mrs R(obert) Lee (1791–1856) to new knowledge of natural history has focused on her book-length publications concerning West Africa, including its preparations in the field for her undertaking of The Fresh-Water Fishes of Great Britain. The nine chapters and their lessons therefore bring to serious critical attention Sarah's multiple contributions to cross-Channel natural history-making in her published works from 1825 until her death. They also inspire the recuperation of other women in the first half of the nineteenth century at work and publishing in science in at least two language cultures. Chapter findings individually and collectively, as gathered together below, then only magnify the main questions of this book. Why and how, indeed, has Sarah remained so firmly in the blind spots of expert Anglophone and Francophone critical inquiry in the disciplines covered in the introduction, and despite gender, transnational and interdisciplinary lenses? Her works plainly added to major discipline fields, and in the case of (modern) ichthyology and anthropology were in their vanguard. The imprimaturs of Cuvier and Humboldt affirmed their first-ranking, original qualities. Sarah's works also eminently proved the rule that a woman could exist, thrive and regularly publish (expert) natural history in the period. But her corpus also demonstrated why the best modern (inter-)disciplinary inquiry in the history, geography and cultures of nineteenth-century British, French and European science will fail to accommodate its expertly multi-genre, intermedial hybridity. Set assumptions govern and determine who and what constitutes ‘serious’ contribution to science of the period, also informing science and its histories today. The introduction highlighted the benchmarks that consolidate scientific endeavour in the first half of the nineteenth century by which Sarah cannot be seen. They are modelled by ‘genteel’ and national(istic) standards compounding the (professionalised) thrall of modern discipline distinctions imposed retrospectively upon ‘serious’ natural history and earlier ‘naturalists’ as its makers in consequence. The nine chapters individually and together challenge modern critics to pay much closer attention to pre-1850 context(s) for broad-church natural history on the one hand, and on the other hand to the latter's foundational basis for ‘new’ nineteenth-century scientific specialisms, such as ichthyology, anthropology and ethnography in which Sarah was a remarkable forerunner irrespective of her sex.