Which one of the following is a chordate but not a vertebrate :-

Options

A. Scoliodon
B. Hag Fish
C. Amphioxus
D. Star fish

Answer

To solve the question "Which one of the following is a chordate but not a vertebrate?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Terms**:
- Chordates are animals that belong to the phylum Chordata, which includes all animals that have a notochord at some stage of their development.
- Vertebrates are a subphylum of chordates that have a backbone or spinal column.

2. **Evaluate the Options**:
- **Option 1: Squalodon (Indian dog shark)**:
- Squalodon is a type of shark, which is a vertebrate. Therefore, this option is incorrect.

- **Option 2: Hagfish**:
- Hagfish are also classified as vertebrates, despite their unique characteristics. Thus, this option is also incorrect.

- **Option 3: Amphioxus**:
- Amphioxus, also known as lancelets, are considered chordates but do not have a backbone, making them invertebrates. This option is correct.

- **Option 4: Starfish**:
- Starfish are not chordates; they belong to the phylum Echinodermata. Therefore, this option is incorrect.

3. **Conclusion**:
- The only option that is a chordate but not a vertebrate is **Amphioxus**.

### Final Answer:
The correct answer is **Amphioxus**.