The inhabitants of Śālmalīdvīpa (Salmalidwipa; the island of Salmali), are said to have been also divided in caturvarṇa (chaturvarna; four castes) like Brāhmaṇa (Brahmana), Kṣatriya (Kshatriya), Vaiśya (Vaisya), and Śūdra (Sudra). Iṣudhara(Ishudhara) was one of these four castes, probably identical to the Śūdra (Sudra) in our varṇa-system .
This term, Iṣudhara, is probably referred to as Iṣandhara (Ishandhara) in the reading of Bhāgavatapurāṇa (Bhagavatapurana).
[See Iṣandhara]