crinoids

例句：

1. 1. These crinoids are found in the ocean depths and are known for their unique shells.
   这些海葵生活在海洋深处，以其独特的壳而闻名。
2. 2. The crinoids were used by ancient civilizations as a source of food and medicine.
   古代文明用海葵作为食物和药材的来源。
3. 3. Scientists have been studying the behavior of these crinoids to better understand marine ecosystems.
   科学家研究这些海葵的行为，以更好地了解海洋生态系统。