Today I found a masonry / steel mesh support in a crawl space under the bathroom. The floor joist were ordinary wood joists. The concrete is bowed downward along with the mesh. I am not familiar with this type of set up. Can I get some comments? Thanks.
Does the top of the floor look okay? If so they probably laid over it with heavy sheathing, which should be okay.
Older home with Tile floor?
The sub floor is covered with vinyl flooring. It is stable and solid to walk on. I guess my initial concern was with the apparent bowing of the cement but I guess it likely looked like that soon afeter it was poured in 1959. Don’t see very many like that here. Thanks for your reply.
I’m surprised to hear of a crawlspace in FL 
This is common in older homes beneath tile floors. It’s also the same method used for heart-extensions in masonry fireplace systems where the home is on a raised foundation.
The weight of the wet concrete created the “bowing” you were referring to. It cured in that position rather than becoming distorted over time.
As others stated, it almost certainly had tile at one time. At least it was designed for tile and they changed their mind perhaps after money got tight.