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 Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection is the title of a joint presentation of two scientific papers to the Linnean Society of London on 1 July 1858: "On The Tendency of Varieties to Depart Indefinitely from the Original Type" by Alfred Russel Wallace and an "Extract from an unpublished Work on Species" from Charles Darwin's "Essay" of 1844, together with an "Abstract of a