1. The tubercle is contrasted with placoid and ganoid scales.

2. The primary categories of fish scales are placoid, cosmoid, ganoid, cycloid and Ctenoid scales

3. Unlike sturgeon-derived caviar, which contains ganoid scales, Bowfin fish have cycloid scales, making them a naturally kosher product.

4. Compare with ganoid and placoid ‘The body is covered with small Ctenoid scales that extend well onto the dorsal and anal fins.’

5. I tried to follow Agassiz's scheme of division into the order of Ctenoid s and ganoids, with the result that I found one of my species of side-swimmers had cycloid scales on one side and Ctenoid on the other.