- Perhaps you were looking for the Scaly-foot gastropod snail that employ metal in its shell ..?
Scaly foot is a bird ailment that is common among finches, parakeets (budgies), and canaries. It is caused by mites burrowing into the animal's flesh. The tracts made by the mites within the skin cause scaly lesions. Scaly face is also caused by the same mite responsible for scaly foot in budgies.
Commonly known as scaly face, scaly legs, or tassel foot, knemidocoptiasis affects primarily the face and legs of birds around the world worldwide and can be fatal. 
Knemidocoptic mange [neʺmĭ-do-kopʹtik mānj]
From the Latin manducare (to itch), mange is a skin disease caused by mites in domestic and wild animals. Knemidocoptic, from the Greek knemid (greave, a piece of armor that protects the leg) and koptein (to cut), refers to the morphology and pathogenesis of mites of the genus Knemidocoptes, which are burrowing mites of birds. 
This article incorporates public domain text from the CDC as cited
- http://www3.sympatico.ca/davehansen/scaly.html - Describes the infection and treatment possibilities.