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Show 44 PROF. T. H. HUXLEY ON CERATODUS FORSTERI. [Jan. 4, process of the skull-an articulation which, in Prof. Gegenbaur's view, represents the primitive attachment of the mandibular arch, but, in m y apprehension, is an altogether secondary connexion. I a m indebted to Dr. Gunther for a foetus of Notidanus (Heptan-chus) cinereus in excellent condition ; and the examination of the skull (fig. 9), which presents all the characteristic features of the adult*, has confirmed the suspicion which I previously entertained, that the Notidanus cinereus. Left lateral view of tbe skull. Letters as in the preceding figures. VII, the posterior division of the portio dura. skull of Notidanus, though fundamentally of a low type, is greatly modified so far as the jaws are concerned. What first led m e to suspect that this might be the case was the backward position of the articular end of the suspensorium and the relative length of the g a p e - features in which the skull of Notidanus differs from that of ordinary Selachians as an old frog differs from a young one. The palato-quadrate cartilage of Notidanus has an inward process (p), which lies in a strong ligamentous band, by which it is attached to the skull between the optic and trigeminal foramina. This answers to the pedicle of the suspensorium in the Amphibia. From this point the palato-quadrate cartilage extends backwards, as a laterally compressed deep plate, the posterior and inferior extremity of "which gives attachment to the mandible. The dorsal and anterior angle of this plate is attached only by ligament to the postorbital process, in the foetus, but appears to articulate therewith in the adult. I think that there can be no doubt that this upward and backward extension of the palato-quadrate cartilage answers to the otic process in the amphibian. It has similar relations to the posterior division of the seventh nerve ; and between it and the hyoidean arch lies the * See Gegenbaur, op. cit. |