The Collaborative International Dictionary of English v.0.48:
Pyx \Pyx\, n. [L. pyxis a box, Gr. pyxi`s a box, especially of
boxwood, fr. py`xos the box tree or boxwood. See Box a
receptacle.] [Written also pix.]
1. (R. C. Ch.) The box, case, vase, or tabernacle, in which
the host is reserved.
2. A box used in the British mint as a place of deposit for
certain sample coins taken for a trial of the weight and
fineness of metal before it is sent from the mint.
3. (Naut.) The box in which the compass is suspended; the
4. (Anat.) Same as Pyxis.
Pyx cloth (R. C. Ch.), a veil of silk or lace covering the
Trial of the pyx, the annual testing, in the English mint,
of the standard of gold and silver coins. --Encyc. Brit.