Pteraspis
a genus of Placodermi, having the cephalic shield finely grooved and composed of seven pieces. It had a rostrum in front, and its lateral angles were produced so as to form short cor- So far as is known, it is the most ancient fish form, two species being nua.
PTEROSAURIA known from the Upper Silurian, and six from the Lower Devonian of Orkney and Perthshire, Scotland.