The Collaborative International Dictionary of English v.0.48:

Petalosticha \Pet`a*los"ti*cha\, PROP. n. pl. [NL., from Gr.
   pe`talon a leaf + sti`chos a row.] (Zool.)
   An order of Echini, including the irregular sea urchins, as
   the spatangoids. See Spatangoid.
   [1913 Webster]