Which one is not a coelenterate?

Options

A. Sea Fan
B. Sea Feather
C. Sea Cucumber/Lily
D. Sea Pen.

Answer

To determine which organism is not a coelenterate (or cnidarian), we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Coelenterates**: Coelenterates, also known as cnidarians, belong to the phylum Cnidaria. This group includes organisms such as jellyfish, corals, and sea anemones. They are characterized by their radial symmetry and the presence of specialized cells called cnidocytes.

2. **Analyzing the Options**:
- **Option A: Sea Fan (Georgonia)**: Sea fans are indeed members of the phylum Cnidaria and belong to the class Anthozoa. Therefore, this option is a coelenterate.

- **Option B: Sea Feather**: Similar to sea fans, sea feathers are also classified under the class Anthozoa within the phylum Cnidaria. Thus, this option is also a coelenterate.

- **Option C: Sea Cucumber (Kukumaria)**: Sea cucumbers are marine animals that belong to the phylum Echinodermata, not Cnidaria. Therefore, this option is not a coelenterate.

- **Option D: Sea Pen (Ptilota)**: Sea pens are members of the phylum Cnidaria and belong to the class Anthozoa. Hence, this option is a coelenterate.

3. **Conclusion**: After analyzing all the options, we conclude that the organism that is not a coelenterate is **Option C: Sea Cucumber**.

### Final Answer:
**Option C: Sea Cucumber** is not a coelenterate.

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