Nectocaris was a weird creature which might have been a cephalopod. The image on the left shows an earlier idea of Nectocaris, but now they believe that the image on the right would be what Nectocaris really looked like.
When Walcott first discovered Nectocaris in the Burgess Shale, he never had time to study it. Then, later, someone described it to be an arthropod. Last year, in 2010, someone described it to be an early cephalopod.
Fossil evidence shows that mud must have gotten into the gills, so Nectocaris was probably a nektobenthic creature, meaning that it lived at the bottom, but swam above the sediment.
Nectocaris was probably either a predator or a scavenger, grabbing food with its two tentacles. Scientists aren't exactly sure if cephalopods started out with two tentacles then they evolved more over time, or if Nectocaris's two tentacles were just made up of its other tentacles.