Bought a new house. Basement slab has writing on it: "Do not Cement"

So, I want to install a small bathroom in my new house, and I wanted to put it where there's already an existing drain. However, I just noticed that on the slab, there's very washed out writing that says "Do not cement," and something else that's too difficult to decipher. And from the writing there's an arrow pointing to the drain. Any idea what this is about? If it helps, the house is very old. It was built in the 30's.

Here's a picture: http://imgur.com/MSffTvc

You can barely see the writing in the area painted red, to the right of the drain.