326 E. T. NEWTON ON TWO CHOLEROID JAW3 FROM 



35. On two Chim^rotd Jaws from the Lower Greensand of New 

 Zealand. By E. Ttjlley Newton, Esq., F.G.S., of H.M. 

 Geological Survey. (Bead June 7, 1876.) 



(By permission of the Director-General of H.M. Geological Survey.) 

 [Plate XXI.] 



Having been working for some time past at the Cretaceous Fishes, 

 my interest has been especially centred in the group of the Edapho- 

 dontidae ; for the specimens belonging to this group, which have 

 been brought to light within the last few years, have much enlarged 

 our knowledge of these peculiar forms of fossil fishes. The general 

 results of my examination of this group, will shortly be pub- 

 lished ; and in the present communication it is only proposed to 

 consider two specimens from the Lower Greensand of New Zealand, 

 which have been deposited in the British Museum by Dr. Hector. 

 My attention was first directed to these specimens by Mr. W. Davies, 

 of the British Museum, when I was examining the fine series of 

 Chimaeroid jaws now in the national collection. 



One of these New-Zealand specimens is the right mandible of a 

 species of Ischyodus already known to us from the Gault of Folke- 

 stone ; and the second is a small right maxilla, which is altogether 

 new and appears to be generically distinct from any of the fossil 

 forms hitherto described. 



Before considering the peculiarities of the mandible, it will be ne- 

 cessary to enter into some explanation and description of the species 

 to which it is referred. 



It appears that the late Prof. Agassiz, some years ago, saw in the 

 Earl of Enniskillen's collection of fossil fishes, a ChimEeroid mandi- 

 ble from the Gault of Folkestone, which he named, in manuscript, 

 Chimcera brevirostris. Subsequently, in his ' Poissons Fossiles ' 

 (1843)*, he alluded to this specimen under the same specific name, 

 placing it in his subgenus Ischyodon f ; but, most unfortunately, he 

 gave no description or figures. Since the publication of that 

 standard work of fossil ichthyology, several examples of Ischyodus- 

 mandibles have been obtained from the Gault, nearly all of which 

 appear to belong to one species. These mandibles have generally 

 been referred to Agassiz's /. brevirostris, simply because they were 

 the only forms of Ischyodus known from the Gault ; but the want of 

 a figure or description of the original specimen left the matter in 

 great uncertainty. 



At the request of my colleague, Mr. Etheridge, the Earl of Ennis- 

 killen has very kindly sent the original type specimen of Agassiz's 

 /. brevirostris to the Museum of Practical Geology for examination 

 and comparison ; and I am now therefore enabled to give for the first 



* Becherches sur les Poissons Fossiles, iii. p. 344. 



t Agassiz provisionally adopted Sir Philip Egerton's genus Ischyodus, with 

 fhe aboA'e modification. 



