The Collaborative International Dictionary of English v.0.48:

Priapulacea \Pri*ap`u*la"ce*a\, n. pl. [NL. See Priapism.]
   (Zool.)
   A suborder of Gephyr[ae]a, having a cylindrical body with a
   terminal anal opening, and usually with one or two caudal
   gills.
   [1913 Webster]