What word has a plural that itself takes a plural (a "pluralses")?

language/english/spelling/plurals/plural.of.plural New

New entry, edited from material collected for the archive and not yet in a released version.

Problem

What word has a plural that itself takes a plural (a "pluralses")?
[ Editor: problem statement reconstructed from the postings. ]

Show solution

[ Editor: from the crossword-games (Scrabble) mailing list, November
  1994; the word lists meant are those used for Scrabble. ]

I'm afraid I'm the CIRRI culprit.  However, the word I was thinking
about is even better:  CERCUS CERCI CERCIS CERCISES

-- Charles Goldstein <scrabble@netcom.com>

Unfortunately, while these are all acceptable words, CERCIS is not
listed as a plural for CERCI.  :-(

-- John Chew <jjchew@math.utoronto.ca>