(under subclass 321.6) Apparatus wherein at least one membrane is, (a) generally tubular, (b) noncylindrical in defining a cross section (said cross section being taken perpendicularly to the central axis of the tube) which is nonannular (e.g., inner and/or outer surface(s) define noncircular cross section, and (c) not coiled.
(1) Note. A coiled flattened membrane tube is provided for in subclasses 321.74 and 321.83.
