The Collaborative International Dictionary of English v.0.48:

Peritricha \Pe*rit"ri*cha\, n. pl. [NL., fr. Gr. peri` about +
   ?, ?, hair.] (Zool.)
   A division of ciliated Infusoria having a circle of cilia
   around the oral disk and sometimes another around the body.
   It includes the vorticellas. See Vorticella.
   [1913 Webster]