There are two reasons why horse dung sea urchins are bitter. They put too much alum, and the sea urchin will melt after a while. In order to keep the shape of sea urchins, many processing factories put some alum, but some manufacturers may put too much alum, which will make sea urchins bitter, and may also meet mature female sea urchins, because some mature female sea urchins contain this bitter substance in their ovaries, which is said to be a bitter amino acid.

The shell of the horse dung sea urchin is a solid hemisphere with a diameter of 30 to 40 mm and a maximum of 60 mm, and its mouth is low, slightly convex and flat. The width of the tread area is equal to that of the middle tread area, but the expansion of the middle tread area is slightly higher than that of the tread area, so the shell shape is a smooth regular pentagon close to a circle from the mouth.

Widely distributed in the world's oceans, vertical distribution can be seen from intertidal zone to 5000 meters deep sea. There are about 800 species of sea urchins in the world, which are widely distributed in China's coastal areas, from the Yellow Sea and Bohai Sea in the north to the coastal areas of Zhejiang and Fujian in the south. Almost all the resources are distributed in the north and south coasts, but the resources are scattered.