Pagurus Usually, a few new species are discovered each year. The following list is current : The following are all "nomina nuda". They have never been validly described as new species, but only mentioned under these names: Pagurus Pagurus is a genus of hermit crabs in the family Paguridae. Like other hermit crabs, their abdomen is not calcified and they use snail shells as portable homes. These marine decapod crustaceans are omnivorous, but mostly prey on small animals and scavenge carrion. "Trigonocheirus" and "Pagurixus" used to be considered subgenera of "Pagurus", but the former is nowadays included in "Orthopagurus", while the
On the Origin of Species an incipient species" and that "species are only strongly marked and permanent varieties". He argues for the ubiquity of variation in nature. Historians have noted that naturalists had long been aware that the individuals of a species differed from one another, but had generally considered such variations to be limited and unimportant deviations from the archetype of each species, that archetype being a fixed ideal in the mind of God. Darwin and Wallace made variation among individuals of the same species central to understanding the natural world. In Chapter III, Darwin asks how varieties "which I have called incipient species"