The malleus of a rotifer of the species 'Brachionus urceolaris' ('fig. c-d').
Source: Hudson, C.T., Memoirs: An Attempt to re-classify the Rotifers in Quarterly Journal of Microscopical Science 1884 s2-24, pages 335-356. http://en.wiktionary.org/wiki/File:Trophi_of_Brachionus_urceolaris.png
Author: C.T. Hudson