330 E. T. NEWTON ON TWO CHIM^ROID JAWS FROM 



Geol. Surv. Dec. 6, pi. i. fig. 8) ; but this resemblance is more appa- 

 rent than real. 



Concerning the maxilla of Ganodus, one would like to be better 

 informed. Agassiz says (' Poissons Possiles,' vol. iii. p. 339) " that 

 the upper jaw of this genus resembles that of Ccdlorhynchus ; but its 

 external face, in place of being entirely concave, presents only a 

 deep groove along the external part, and the remainder is convex." 

 The New-Zealand specimen does not agree with this description, nor 

 with the figures which are given. Concerning the mandibular teeth 

 Agassiz goes on to say that they are near together and united into 

 a protuberance covered by a bony layer, and that they are placed 

 so obliquely as to be parallel with the dcntary margin. 



Prom these considerations, I think it will be obvious that the 

 New-Zealand specimen cannot be referred to either Ischyodus, Eda- 

 pliodon, or Elasmodus, and also that we should not be justified in 

 placing it in the genus Ganodus ; for it seems extremely improbable 

 that teeth placed obliquely in the mandible should wear a single 

 maxillary tooth into longitudinal grooves. 



A comparison of the New-Zealand specimen with the maxilla of 

 Ccdlorhynchus antarcticus shows that, although there are minor dif- 

 ferences, yet in all their chief joints they are remarkably alike. 

 Their general form and size closely agree. In both there is but a 

 single tooth, forked anteriorly and covered by the bone posteriorly. 

 The greatest differences between the two are these : the tooth of 

 the New-Zealand maxilla is flatter, larger, and has longer anterior 

 processes than that of C. antarcticus, the tooth of the latter being- 

 more rounded and not approaching so nearly to the borders of the 

 bone, while the anterior portion is much less deeply indented. 



Each mandible of C. antarcticus possesses but one tooth ; and it is 

 this which cuts out the indentation in the front of the maxillary 

 tooth, thus forming the two processes. The outer margin of the 

 mandible, although not armed with teeth, is trenchant and wears 

 away the outer surfaces of the maxillary bone and tooth. The inner 

 or symphysial edge of the maxillary tooth stands above the surface 

 of the bone, so that when the two maxillse are together there is a 

 groove between the teeth. This conformation is markedly shown 

 in the New-Zealand maxilla. 



The differences above-mentioned between the maxilla of C. antarc- 

 ticus and the New-Zealand fossil are of such a character that they 

 can scarcely be regarded as of more than specific value ; and it is 

 suggested that the name of the Director-General of the New-Zealand 

 Survey, who brought the specimen to this country, should be as- 

 sociated with it as a specific appellation, and that this Chima3roid 

 fish should be known as Ccdlorhynchus Hectori. 



With regard to the geological horizon from which the two speci- 

 mens constituting the subject of the present communication were 

 derived, the only information I have been able to obtain is, that 

 they were found, together with other fish remains, imbedded in a 

 fine conglomerate, believed to be of Lower Greensand age, which 

 occurs at Amuri Bluff, New Zealand. 



