ON A NEW PISH FROM THE LOWER CHALK OF DOVER. 439 



27. Description of a New Fish from the Lower Chalk of Dover. 

 By E. T. Newton, Esq., E.G.S., of H.M. Geological Survey. 

 (Read March 20, 1878.) 



[Plate XIX.] 



In a former communication to this Society* I described certain 

 specimens of fish-remains from the Cretaceous rocks of Britain 

 which I believe to be the English representatives of PortJieus and 

 Ichihyodectes. In the present paper I have described another Cre- 

 taceous fish, belonging, as I think, to Daptinus, a third American 

 genus not hitherto recognized in this country. 



The specimen, which is imbedded in a block of Grey Chalk, was 

 obtained from Dover by Mr. J. S. Gardner, and is now in the 

 British Museum (no. 47250). It has been admirably developed 

 under the careful superintendence of my esteemed friend Mr. "W. 

 Davies, to whom I am much indebted, as also to Dr. H. Woodward, 

 for the facilities afforded me for the examination of this fossil. It 

 consists of a skull with the facial and opercular bones of the left 

 side almost perfect, and retaining very nearly their natural rela- 

 tions to each other. The surfaces of the bones are mostly abraded ; ■ 

 but where they remain apparently intact, they exhibit no kind of 

 ornamentation, except the radiating lines indicative of the direction 

 of growth, which are commonly to be met with on teleostean fish- 

 bones. In a side view (fig. 1) four vertebras are to be seen ; but 

 probably two others intervene between the anterior of these and 

 the skull, and most likely two more are overlain by the bone marked 

 pt.tem. 



The teeth have long, hollow roots, sunk in deep sockets, and were 

 replaced vertically — characters which are displayed by a fortuitous 

 fracture of the maxillary bone. The praemaxilla and maxilla are 

 firmly articulated with each other, the former being a very short, 

 but deep, bone. The symphysis of the lower jaw is deep. In all 

 these particulars this specimen closely resembles Portheus and Ichihyo- 

 dectes ; and its close affinity to them is further shown by the form of 

 the vertebras. Bearing these characters in mind, and noticing also 

 the regularity of the teeth, it seemed at first that this specimen must 

 belong to the genus Ichthyodectes ; but a comparison with the species 

 of that genus showed that, in certain particulars in which it differed 

 from them, it agreed with Cope's description of Daptinusf. The 

 chief difference given by Prof. Cope as existing between Ichthyodectes 

 and Daptinus is that the latter has the crowns of the teeth much 

 compressed and with knife-like edges. Now our specimen agrees 



* Quart. Journ. Geo!. Soc. vol. xxxiii. p. 505. 



t United-States Geol. Surv. Terr. vol. ii. Cret. Vertebrate, p. 213. 



