The soft and spongy layer of skin over the visceral hump of molluscs is known as:

Answer

To solve the question regarding the soft and spongy layer of skin over the visceral hump of molluscs, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Body Structure of Molluscs**:
- Molluscs are part of the phylum Mollusca, which is the second largest phylum in the animal kingdom.
- Their body is generally divided into three main parts: the head, the muscular foot, and the visceral hump.

2. **Identify the Visceral Hump**:
- The visceral hump is a significant part of the mollusc's body, housing the internal organs.

3. **Recognize the Layer of Skin**:
- The question specifically asks about a layer of skin that is soft and spongy, located over the visceral hump.

4. **Determine the Correct Term**:
- The layer of skin that covers the visceral hump is known as the "mantle." This mantle is responsible for various functions, including the secretion of the shell in shelled molluscs.

5. **Conclude the Answer**:
- Therefore, the soft and spongy layer of skin over the visceral hump of molluscs is called the "mantle."

### Final Answer:
The soft and spongy layer of skin over the visceral hump of molluscs is known as the **mantle**.

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