Maa Siddhidatri is definitely the ninth avatar of maa Durga and is also worshipped over the 9th day of navratri. Ma Siddhidatri is represented with 4 arms sitting down on a beautiful lotus flower. • Bow and arrow in her next still left decreased hand symbolizes character like Lord Rama.  https://www.youtube.com/watch?v=S1HpMpEww4Q