The Collaborative International Dictionary of English v.0.48:

Scamillus \Sca*mil"lus\, n.; pl. Scamilli. [L., originally, a
   little bench, dim. of scamnum bench, stool.] (Arch.)
   A sort of second plinth or block, below the bases of Ionic
   and Corinthian columns, generally without moldings, and of
   smaller size horizontally than the pedestal.
   [1913 Webster]