The mention of dragon(s) in 華陽國志

Hi, I'm currently doing some research on dragon bones and came across this passage in the 3rd volume of Huáyáng Guó Zhi by Chang Qu, and the translations I've found don't seem to agree : is this story about one cloud dragon (Yunlong) trying to reach Heaven's Gate, or several dragons ? Also, does "Yunlong" refer here to a type of dragons or is it the name of this particular dragon ? Thanks in advance for your help !

"五城縣 郡東南。有水通於巴。漢時置五倉,發五縣民,尉部主之。後因以為縣。出龍骨。云龍升其山,值天門閉,不達,墮死於此。後沒地中。故掘取得龍骨。"

https://preview.redd.it/o973egnhypme1.png?width=936&format=png&auto=webp&s=72fd61237d247fad18f20c85f7bbfec197590cdc