Fig. 34.
MAXILLARY BONE?
(One fourth nat. size, linear.)
Of the upper maxillary bones of the Asterolepis, I only know that a considerable fragment of one of the pieces, recognized as such by Agassiz, has been found in the neighborhood of Thurso by Mr. Dick, unaccompanied, however, by any evidence respecting its place or function. It exhibits none of the characteristic tubercles of the dermal bones, and no appearance of teeth; but is simply a long bent bone, resembling somewhat less than the half of an ancient bow of steel or horn,—such a bow as that which Ulysses bended in the presence of the suitors. By some of the Russian geologists this bone was at first regarded as a portion of the arm or wing of some gigantic Pterichthys. In the accompanying print (fig. 34) I have borrowed the general outline from that of a specimen of Professor Asmus, of which a cast may be seen in the British Museum; while the shaded portion represents the fragment found by Mr. Dick. The intermaxillary bones, like the dermal plates of the lower jaw, were studded by star-like tubercles, and bristled thickly along their lower edges with the ichthyic teeth, flanked by teeth of the reptilian character. The opercules of the animal consisted, as in the sturgeon, of single plates (fig. 35) of great massiveness and size, thickly tubercled outside, without trace of joint or suture, and marked on their under surface by channelled lines, that radiate, as in the other plates, from the centre of ossification. That space along the nape which intervened between the opercules, was occupied, as in the Dipterus and Diplopterus, by three plates, which covered rather the anterior portion of the body than the posterior portion of the head, and which, in the restoration of Osteolepis, (fig. 13,) appear as the plates, 9, 9, 9. I can say scarce any thing regarding the lateral plates which lay between the intermaxillaries and the cranial buckler, and which exist in the Osteolepis, fig. 13, as the plates 2, 4, 5, 6, and 7; nor do I know how the snout terminated, save that in a very imperfect specimen it exhibits, as in the Diplopterus and Osteolepis, a rounded outline, and was set with teeth.
Fig. 35.
INNER SURFACE OF OPERCULUM OF ASTEROLEPIS.
(One fifth nat. size, linear.)
