This group gathers Mollusks subcategory members belonging to the class Gastropoda, the snails and slugs, by far the largest and most diverse class of mollusks and, after the insects, one of the largest groups of animals of any kind by number of described species. It spans shelled marine, freshwater and terrestrial snails such as the garden snail, the whelks and conches, the limpets, clinging to intertidal rocks by suction, and the brightly patterned cowries, alongside slugs, which have reduced or entirely lost the external shell their snail relatives carry, and the sea slugs and nudibranchs, marine gastropods often displaying some of the most vivid coloration found anywhere in the animal kingdom, warning coloration in many species that advertises genuinely toxic or unpalatable chemical defenses absorbed from prey. Nearly every gastropod moves by rippling muscular contractions along a broad, flat foot lubricated by a layer of mucus, the same slime trail every land snail and slug leaves behind as it travels.