Today I was performing a fish head dissection to investigate the gas exchange process in biology. Then when I opened the mouth I noticed these small hard structures at the base, I assume they may be a form of teeth that allows the fish to grind hard shells of invertebrates and plant matter. Yet I was curious as to why some fish have this and others don't and what exactly it's function is. Also if you have a name I would highly appreciate it as I can label it in my lab book. Thank you so much for your time.