192 Proceedings of the Royal Physical Society. 



what these remains were Mr Kirkby does not state. The 

 specimen 1 now show is, therefore, the third recorded instance 

 of the occurrence of Ctenodus in rocks belonging to the Cal- 

 ciferous Sandstone Series, and the first of its occurrence in 

 the oil shales of this district. The specimen shows a single 

 tooth, only part of which, however, is visible ; the remainder 

 is so imbedded in the ironstone as to offer little hope of 

 separating the two. It will be possible, however, to remove 

 the tooth by means of acid, and from the mould thus left 

 to obtain a cast of the remainder of the tooth. From the 

 part visible, the tooth appears to have nine ridges moderately 

 tuberculated throughout, the ridges growing deeper and 

 further apart as they approach the outer margin. Asso- 

 ciated with the tooth are several bones of the head occu- 

 pying their natural position. Similar specimens have been 

 found in the coal measures of Northumberland, but they are 

 decidedly rare. This specimen also shows the greater part 

 of the operculum of the fish — a roundish, thickened bone 

 measuring about 4 inches across. From data supplied by a 

 very small but tolerably complete specimen of Ctenodus, de- 

 scribed by Mr Atthey, the individual to which the large 

 operculum belonged, was probably not less than five feet in 

 length. Ctenodus possessed well ossified ribs, and in the 

 present specimen several portions of ribs are to be found. 

 One of these is of special interest, as showing where a rib 

 has been fractured, and afterwards repaired in the living 

 fish. That the Ctenodus to which this tooth and these bones 

 appertained was not specifically identical with any of the 

 coal measure forms is almost certain, and when the entire 

 tooth is visible it may be expected to disclose characters 

 sufficient to distinguish it from previously described species. 

 As the head bones, however, belong presumably to the same 

 fish as the tooth, and as the unravelling of the complex re- 

 lationships of these could only be attempted satisfactorily by a 

 specialist in fossil fishes, I do not propose affixing a specific 

 name to those remains, but will leave their further descrip- 

 tion to Dr Traquair, who is at present collecting material 

 for what will, no doubt, form a satisfactory treatment of the 

 genus Ctenodus. 



