Help with Unknown bone

[PODIGGER]

I have had this piece of heavy bone for a couple of weeks and have been trying to come up with an ID before putting in the unidentified category.  It was found in the Peace River, FL.  When I picked it up I found it to be very solid and heavy.  It has a curvature/roundness to it similar to what I have found in pieces of tusk, along with what looks like an outer ring of "bark".  The ends show no sign of Schreger lines to indicate ivory.  It also has the honeycomb type look on the inner side that one would expect from bone.  I haven't been able to find anything to compare it to.

 

 Overall it measures 168 mm long x 104 mm wide x 45 mm thick or 6 1/8" x 3 7/8" x 1 5/8".  The width tapers to 65 mm and the thickness tapers to 22 mm at the smaller end.  It also appears to curve slightly as it tapers.  Could it be some type of horn?   Any help would be greatly appreciated, Thanks !

 

 

 

 

 

 

 

 

 

 

 

 

[val horn]

? Tortise large?

[PODIGGER]

Thanks for the response. Could be a possibility. What would be the “shell “ exterior in this case is extremely smooth and the curvature doesn’t seem right to me.