sclerite

from WordNet (r) 3.0 (2006)

sclerite
    n 1: hard plate or element of the exoskeleton of some arthropods

from The Collaborative International Dictionary of English v.0.48

Sclerite \Scle"rite\ (skl[=e]"r[imac]t), n. (Zool.)
   A hard chitinous or calcareous process or corpuscle,
   especially a spicule of the Alcyonaria.
   [1913 Webster]