In 1942, after the disappearance of his Guru, Srila Sarasvati Prabhupada, Swami Bon voted for Swami Bhakti Vilas Tirtha to be the next Acharya of the Gaudiya Math.
The deities invoked are Sharada, Ganesha, Sarasvati, Maccha, Kacchap, Varaha, Narasimha, Vaman, Parashuram, Ram and Krishna Avatars of Vishnu, Bhairunath, Ramdev, Shani, Surya and Chandrama.
Saraswat Brahmins are Brahmins who lived on the banks of the former Sarasvati River that once flowed in northern India, joining the Ganges and Yamuna in Prayag.
The rivers mentioned in the 7th Mandala are the Sarasvati, Asikni, Parusni and possibly the Yamuna (in 7.18.19 the name of a helper of Indra, maybe also the name of a woman or goddess).