I think this is a section of a mouthplate from a ray, quite possibly a cow-nosed ray. Go to www.elasmo.com Select Extant Dentitions In the "select species" box, scroll down to Rhinoptera bonasus, at the bottom of the list That looks to me like what you have. Also, from the elasmo.com home page, select Myliobatoid Teeth Scroll through those pictures and you will find some similar things Paul M.