You're thinking of the Mid-Atlantic Ridge. It's a ridge, not a trench, and it runs down the center of the Atlantic Ocean basin, not just curves down the middle.

Here's a breakdown:

* Mid-Atlantic Ridge: A massive underwater mountain range formed by tectonic plate divergence (the plates moving apart). It's a key feature of the Atlantic Ocean basin.

* Trench: A deep, narrow depression in the ocean floor, often found near subduction zones (where one plate slides under another).

So, the Mid-Atlantic Ridge is a ridge, not a trench, and it runs along the entire length of the Atlantic Ocean basin, not just curves down the middle.