Atri's classification of Brahmanas - Source: PV Kane's History of Dharmśastra Volume 2 Part 1, pg 131 on the discourse in the Atri Smriti:
1. Deva Brahmana: Bathe daily, do Puja, SandhyaVandanam, homam, honor Aditis (guests) & Vaishvadevas
3. Dvija Brahmana: Twice-born. Studies Vedanta, gives up all attachments, engages in Samkya & Yoga (implying AshtAnga Yoga).
4. Kshatra Brahmana: Fights to defend the motherland.
6. Shudra Brahmana: Sells meat, lac, dyes like Kusumba, milk, ghee, honey
7. Nishada Brahmana: loves meat & fish, thieves & robs, backbiter.
8. Pashu Brahmana: Knows nothing on Brahman but is proud of his birth & sacred thread.
10. Chandala Brahmana: Adharmic, cruel, foolish, does no prescribed rites.
Not in Atri's list: