--> Ferruginous has double "rr" is mispronounced as "r"
Remember double 'RR' in between the strings fe & uginous which should not be misspelled with single 'R'
Wrong Spelling:  fe-r-uginous 
Correct Spelling:  fe-rr-uginous 
Check more misspelled words of Ferruginous to spell it correct.