Banffia could have been a weird relative of Vetulicola, Xidazoon, Ooedigera, and Skeemella. Unlike its relatives, Banffia's tail was twisted up into a spiral. Like all its relatives, it had no jaws and a long tail. The anus is probably the notch at the end of the tail.
Banffia may not have kept its tail twisted into a spiral. It may have just twisted it into a spiral to move downward, then untwisted it and flapped it from side to side to move and go upward. Banffia probably died out because of having a design fault with locomotion. The mudslide buried creatures near the bottom, and if something can't move up fast enough in the water it will fall down to the bottom and get buried by the mudslide.
In this image, Banffia is shown descending alongside an invertebrate chordate called Pikaia, which could have been our earliest ancestor. Banffia probably descended to jump down on its prey and surprise it before it could get away, then suck it up into its jawless mouth.