The Collaborative International Dictionary of English v.0.48:

Onycha \On"y*cha\, n. [NL., from L. onyx, -ychis, onyx, also, a
   kind of mussel, Gr. ?, ?. See Onyx.]
   [1913 Webster]
   1. An ingredient of the Mosaic incense, probably the
      operculum of some kind of strombus. --Ex. xxx. 34.
      [1913 Webster]

   2. The precious stone called onyx. [R.]
      [1913 Webster]

Easton's 1897 Bible Dictionary:

Onycha
   a nail; claw; hoof, (Heb. sheheleth; Ex. 30:34), a Latin word
   applied to the operculum, i.e., the claw or nail of the strombus
   or wing-shell, a univalve common in the Red Sea. The opercula of
   these shell-fish when burned emit a strong odour "like
   castoreum." This was an ingredient in the sacred incense.


U.S. Gazetteer Places (2000):

Onycha, AL -- U.S. town in Alabama
   Population (2000):    208
   Housing Units (2000): 113
   Land area (2000):     0.835126 sq. miles (2.162966 sq. km)
   Water area (2000):    0.005115 sq. miles (0.013248 sq. km)
   Total area (2000):    0.840241 sq. miles (2.176214 sq. km)
   FIPS code:            57024
   Located within:       Alabama (AL), FIPS 01
   Location:             31.221515 N, 86.277694 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Onycha, AL
    Onycha