Prothalium or Prothallium: How To spell?
The word Prothalium is misspelled against Prothallium, a noun meaning "Same as Prothallus."
Prothallium has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings protha & ium which should not be misspelled with single 'L'
Wrong Spelling:  protha-l-ium  Correct Spelling:  protha-ll-ium 
Check more misspelled words of Prothallium to spell it correct.