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 my apprehension, is an altogether secondary connexion. 



I am 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 



AfCi 



Notidanus cinereus. Left lateral view of the skull. 



Letters as in the preceding figures. YII, the posterior division of 



tie portio dura. 



skull of Notidanus, though fundamentally of a low type, is greatly 

 modified so far as the jaws are concerned. What first led me 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 gape — 

 features in which the skull oi 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 an- 

 swers 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 pro- 

 cess, in the foetus, but ajipears 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. 



