What is the third tab of the encyclopaedia?

[OiooNiN]

I got New Leaf two days ago, and I am wondering what the third tab is for?

 

[Bones]

Critters caught from diving, though they're actually grouped in with regular ocean fish at the museum.

 

[OiooNiN]

Thanks! I was so puzzled when I though it was Fish, Bugs and Octopi?!

 

[Superpenguin]

Critters caught from diving, though they're actually grouped in with regular ocean fish at the museum.

They're actually in their own room. They are a part of the Fish Exhibit though.

 

[JurassicJunkie]

Deep-Sea Catches ... Sadly I've not unlocked this part yet