Sigilarid or Sigillarid: How To spell?
The word Sigilarid is misspelled against Sigillarid, a noun meaning "One of an extinct family of cryptagamous trees, including the genus Sigillaria and its allies."
Sigillarid has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings sigi & arid which should not be misspelled with single 'L'
Wrong Spelling:  sigi-l-arid  Correct Spelling:  sigi-ll-arid 
Find more wrongly spelled words of Sigillarid to spell it well.