THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. VII. 



No. XII.— DECEMBER, 1900. 



I. — On Hyperodapedon Gordon/. 



By Prof. EvDOLF Bukckhardt, Ph.D., of the Uuiversity of Basel, Switzerland. 



{Cmitinued from the Novemhcr Number, p. 492.) 



IN the foregoing description I have confined ray remarks to the right 

 side of the skull. The observer will not fail to notice from the 

 figures the disparities existing in the two sides. This asymmetry 

 is particularly conspicuous ventrally, the region from which Huxley 

 principally deduced the arguments in support of his more important 

 speculations. The area of dislocation, the centre of which apparently 

 lies in the crater-like opening of the left prjBsplenial, extends from 

 the left prferaaxillary to the pterygoid in the skull, and as far as the 

 splenial on the lower jaw. Its place of greatest intensity has been 

 marked by a + on the figure, where not only the surface of the 

 bones is most damaged, but where the mandible has been so much 

 compressed that a crest has actually been formed below the row of 

 teeth on its outer wall. 



The splenial too has been displaced ; the pterygoid is broken 

 across ; a deep fissure separates the three inner rows from the 

 regularly placed outer rows of teeth on the palate-bone. 



This dislocation is partly responsible for the deception it caused 

 m the location of the posterior nares, and for the supposed boundary 

 of the palate-bone and the maxillary. Huxle}'^ himself, in his first 

 paper, inaugurates the description of the dentition by stating his 

 inability to find any suture in the roof of the mouth, but he supposed 

 such to exist somewhere in the groove of the hard gum, into which 

 the lower jaw is received when at rest. 



In his second paper he lays particular stress on the fact of there 

 being only a single row of teeth tending in a forward direction on 

 either the palatine or the maxillary. Certainly some of the smaller 

 fragments show no suture within the denticulated space, but there is 

 one which runs parallel with and is situated laterally to the outer- 

 most row of teeth, which can be traced without cutting a cross 

 section through it. 



This leads us to a consideration of the dentition itself. Lydekker 

 was the first to make known the existence of one to two rows of 

 detached teeth on the posterior margin of the oral surface in the 

 lower jaw of the Indian species, next to the palisade-like row of 



DECADE IV. VOr,. VII. — XO. XII. 34 



