CC Madhya 20.294

tṛṭīya-puruṣa viṣṇu — ‘guṇa-avatāra’
dui avatāra-bhitara gaṇanā tāṅhāra
Word for word: 
tṛtīya-puruṣa — the third Personality; viṣṇu — Lord Viṣṇu; guṇa-avatāra — the incarnation of the material quality of goodness; dui avatāra-bhitara — within the two incarnations; gaṇanā tāṅhāra — He is designated.
Translation: 
“The third expansion of Viṣṇu is Kṣīrodakaśāyī Viṣṇu, who is the incarnation of the quality of goodness. He is to be counted within both types of incarnations [puruṣa-avatāras and guṇa-avatāras].