Has the form of a cylindrical tube, slightly curved, and open at both
ends; one extremity closed by four trapezoidal valves attached to the
inner margin, the other end closed by a membrane. The annular ribs which
separate the compartments show its progressive growth. Found buried so
deeply in the fat of marine animals, particularly whales, that only the
operculum and the upper part of the tube are visible. Shell rather
elevated, sub-cylindrical, the partitions rather small and indented; the
spaces or compartments almost quadrilateral; the inferior much more
narrow than the others; the apertures equal and circular; the membrane
which closes the superior forming a tube between the four almost equal
valves of the operculum.
_T. balænarum._ The Whale Tubicinella.
Tubular, with transverse ribs, and a ring-shaped margin; operculum
bottle-shaped.