Note 22 — Chapter XII
Reading edition
I can entertain no doubt that the angular groups of palatal teeth figured by Agassiz and the Russian geologists as those of a supposed Placoid termed the Ctenodus, are in reality groups of the palatal teeth of Dipterus. In some of my specimens the frontal buckler of Polyphractus is connected with the gill-covers and scales of Dipterus, and bears in its palate what cannot he distinguished from the teeth of Ctenodus. The three genera resolve themselves into one.