The Collaborative International Dictionary of English v.0.48:

Paxillus \Pax*il"lus\, n.; pl. Paxilli. [L., a peg.] (Zool.)
   One of a peculiar kind of spines covering the surface of
   certain starfishes. They are pillarlike, with a flattened
   summit which is covered with minute spinules or granules. See
   Illustration in Appendix.
   [1913 Webster]