Cycloidi or Cycloidei: How To spell?

The word Cycloidi is misspelled against Cycloidei, a noun meaning "An order of fishes, formerly proposed by Agassiz, for those with thin, smooth scales, destitute of marginal spines, as the herring and salmon. The group is now regarded as artificial."

Word end with consecutive vowels 'EI' preceded by alphabets 'cycloid' is misspelled as 'I' as letter 'E' is phonetically ignored
Wrong Spelling:  cycloid-i 
Correct Spelling:  cycloid-ei 
Find more incorrect spellings of Cycloidei to spell right way.