Dumviri or Duumviri: How To spell?
The word Dumviri is misspelled against Duumviri, which is plural of "Duumvir"
Duumviri has double "uu" is mispronounced as "u"Remember double 'UU' in between the strings d & mviri which should not be misspelled with single 'U'
Wrong Spelling:  d-u-mviri  Correct Spelling:  d-uu-mviri 
Check more misspelled words of Duumviri to spell it correct.