microthoracidæ

from The Century Dictionary.

• noun A family of holotrichous ciliate infusorians, consisting of small asymmetrical forms, with the mouth in the hinder part of the body, the cilia scattered and sometimes limited to the oral region, and sometimes one or two undulating membranes. It contains several genera, among them being Microthorax, Cinetochilum, and Ancistrum.