Note 20 — THE ASTEROLEPIS, ITS STRUCTURE, BULK, AND ASPECT.
Reading edition
The shaded plate, (a,) accidentally presented in this specimen, belongs to the upper part of the head. It is the posterior frontal plate F, which half-encircled the eye orbit, (see fig. 29;) and I have introduced it into the print here, as in none of the other prints, or of any other specimens, is its upper surface shown.