The image below shows the whole fish.
Cosmoid scales are similar to placoid scales and probably evolved from the fusion of placoid scales.
They consist of two basal layers of bone, a layer of dentine-like cosmine, and an outer layer of vitrodentine. As the fish grows each scale becomes larger as new bone is added to the basal layers. Below is A Queensland Lungfish from the Museum collection. The Diversity of Fishes. Scanning electron micrograph of the cosmoid scales of a Queensland Lungfish.