Malacologie de l'Algérie, ou, Histoire naturelle des animaux mollusques terrestres et fluviatiles recueillis jusqu'à ce jour dans nos possessions du nord de l'Afrique, Paris, Challamel aîné, 1864, Algeria, mollusks, mollusks, fossil, This illustration features a detailed collection of various shell types, identified by unique numbers corresponding to each specimen. The shells vary in shape, size, and texture, showcasing the diversity of marine life. Among the displayed specimens are both spiraled and flat shells, each rendered with precise lines to highlight their distinctive patterns and features. The layout is organized in a grid format, making it easy to compare the different forms. The title at the top indicates that this is Plate XXI, suggesting it is part of a larger work dedicated to the study and classification of mollusks or similar organisms. The scientific exploration of these specimens is evident, reflecting a meticulous approach to natural history documentation.