觀音義疏 2.78

2.78

龍有四種：一、守天宮殿，持令不落人間，屋上作龍像之爾；二、興雲致雨，益人間者；三、地龍，決江開瀆；四、伏藏，守轉輪王大福人藏也，肇師但出三，不出天龍。

There are four kinds of nāgas: first, those that guard heavenly palaces and support them so that they do not fall into the human realm, which is just like making nāga figures on roofs; second, those that raise clouds and bring rain, benefiting the human realm; third, earth nāgas, which dredge rivers and open canals; fourth, hidden-treasure [nāgas], which guard the treasuries of wheel-turning kings and people of great merit. Master Zhao only brought out three, not bringing out heavenly nāgas.