暴腮烏甲 Bristling Cheeks And Black Scales
須臾，至白玉階對國王道：「那妖賊已取來了。」國王下降龍床，與唐僧及文武多官，同目視之。那怪一個是暴腮烏甲，尖嘴利牙；一個是滑皮大肚，巨口長鬚。雖然是有足能行，大抵是變成的人像。须臾，至白玉阶对国王道：「那妖贼已取来了。」国王下降龙床，与唐僧及文武多官，同目视之。那怪一个是暴腮乌甲，尖嘴利牙；一个是滑皮大肚，巨口长须。虽然是有足能行，大抵是变成的人像。
逐句解 Line by line
In a moment they were at the white jade steps, and said to the king, "The fiend-thieves have been fetched."
白玉階 is the same jade stair Pilgrim was standing beside with his arms folded a few passages ago. The report is four characters of plain business.
The king came down from the dragon couch, and with the Tang monk and the officers civil and military looked at them together.
下降龍床 is the king coming down off his throne to look, which is not a small thing for a sovereign to do. 同目視之 puts monarch, monk and the whole bureaucracy at one eye level, all doing the single thing nobody in this kingdom did for three years.
Of the fiends, one had bristling cheeks and black scales, a pointed snout and sharp teeth; the other a smooth hide and a great belly, a huge mouth and long whiskers.
The two halves are set here as one line because they are a single strictly matched sentence, cut across by a printed semicolon: four characters of face against four of body in each. 長鬚 takes cháng, long, not the zhǎng of growing. And the descriptions match the species deposed on the pagoda — scales and teeth for the black fish, whiskers and belly for the catfish.
Though they had feet and could walk, they were on the whole only human shapes they had changed themselves into.
大抵是變成的人像 is the narrator stepping in with a qualification, and it does careful work. What the court is looking at is not a man and not quite a fish but a transformation stopped part way through — which is what the chains through the shoulder-bones were for.
The whole court comes down off the dais to look, and the novel gives the looking four sentences. It is the chapter's one moment of collective, deliberate observation — and everything that went wrong in this kingdom went wrong for want of exactly this.
What they see is described in the vocabulary of a fish market: cheeks, scales, snout, teeth, hide, belly, mouth, whiskers. Then the last sentence adds the thing that makes it uncanny. They walk on feet, and the shapes are borrowed.