Found in Central Florida Backyard

[rockandbone]

We live in a part of Florida that is known to be the only very “hilly” part of the entire state. Which leads me to believe many years ago water filled these natural curves in the land. I often forage for animal bones of animals that have died of natural causes recently, and collect pretty rocks as a hobby. This one threw me for a loop.. bone like color and smoothness.. very circular holes as if something once occupied them.. but a rocky structure underneath. I was hoping for anyone to help me ID what this might be, whether that be a cast, a fossil, or a really neat rock. Was afraid to clean it up because I’m not sure of the ID yet. Thanks for all your help! 

[NaturalSciGuy]

Tough one. A  non-expert eye here. Thinking calcium carbonate matrix, suggestions of polychete or barnacle cluster in structure, but may just be carbonate 'cement' from ancient reef.

[automech]

Agree with @NaturalSciGuy. Not a vertebrate fossil. 

[Fossildude19]

Looks like travertine, to me. 

[EkkerEli]

Geologist in Florida,

Looks to me like some carbonate cemented shell hash.

Reference the attached image and you can probably match any mollusks or casts you can see clearly with collections from Pleistocene or Pliocene shell assemblages.