Dictionary.net

• A fossil cephalopod.

1914 - Nuttall's Standard dictionary of the English language
By Nuttall, P.Austin.

• In geol., a genus of the ammonite family, so named from the shell, which is hooked or bent upon itself.

1874 - Etymological and pronouncing dictionary of the English language
By Stormonth, James, Phelp, P. H.