Dryssena or Dreissena: How To spell?

The word Dryssena is misspelled against Dreissena, a noun meaning "A genus of bivalve shells of which one species (D. polymorpha) is often so abundant as to be very troublesome in the fresh waters of Europe."

Word contains consecutive vowels 'EI' in between alphabets dr & ssena is misspelled as 'Y'
Wrong Spelling:  dr-y-ssena 
Correct Spelling:  dr-ei-ssena 
Explore spell check of Dreissena to spell without errors.