Prostraca or Proostraca: How To spell?
The word Prostraca is misspelled against Proostraca, which is plural of "Proostracum"
Proostraca has double "oo" is mispronounced as "o"Remember double 'OO' in between the strings pr & straca which should not be misspelled with single 'O'
Wrong Spelling:  pr-o-straca  Correct Spelling:  pr-oo-straca 
Find more incorrect spellings of Proostraca to spell right way.