"The zoology of the voyage of H.M.S. Beagle, [vol. 4 of 5]" by Leonard Jenyns is a scientific publication written in the mid-19th century. Focusing on ichthyology, it catalogs and illustrates the fishes collected during the Beagle expedition, giving precise descriptions, measurements, fin-ray formulas, and habitats. The work highlights numerous new species and several new genera, especially from South American shores and the Galapagos, presented with rigorous comparative notes. The opening of the volume sets out the scope: 137 fish species are described, likely only half of what was collected, with many lost in transit; about seventy-five appear new to science, and all Galapagos specimens (fifteen) are both preserved and new. Jenyns details collection localities, breaks down species by major orders and families in tables, and notes particularly high novelty among South American freshwater groups. He explains methods (following Cuvier and Valenciennes), cautions about the difficulty of distinguishing species from varieties, and justifies richly detailed descriptions to prevent taxonomic confusion; Darwin’s color notes (using Patrick Syme’s standards) are emphasized. A systematic table lists each species with its habitat and accompanying plates, after which the treatise begins species accounts—starting with a new Patagonian perch (Perca lævis), several Serranus from the Galapagos and Cape Verde, and other taxa—often including habitat notes, coloration, and careful comparisons. Early sections also name several entirely new genera and note that the collection is deposited in the Cambridge Philosophical Society’s museum. (This is an automatically generated summary.)

The zoology of the voyage of H.M.S. Beagle, [vol. 4 of 5] : $b Fish