Tanais, or the "Cheliferous Slater," a genus of Isopoda (q.v.), of interest as it is the only member of this order, or even of the whole of the Sessile-eyed Crustacea or Leptostraca (q.v.) and Arthrostraca (q.v.), which has a carapace or shield. This structure is usually characteristic of the Stalk-eyed Crustacea or Thoracostraca.