The type of sedimentary rock formed from the remains of coral and sea shells is limestone.

Here's why:

* Coral and sea shells are made of calcium carbonate (CaCO3).

* Limestone is also primarily composed of calcium carbonate.

* Over time, the skeletons and shells accumulate on the ocean floor, and through a process of compaction and cementation, they transform into limestone.

So, the abundant calcium carbonate in the remains of coral and sea shells is the key ingredient that forms limestone!