430 Mr. J. "\Y. Davis 0}i Palteospinax priscus, Egerton. 



opposite extremity of the specimen. The whole surface is 

 covered with minute dermal ossicles or shagreen. 



There are seventv-eight vertebrte present. The second 

 dorsal spine is evidently in its natural position with regard to 

 the vertebrae, and is fixed above the fifty-sixth from the head ; 

 behind there are twenty-two others. The position of the 

 anterior dorsal spine and fin has been somewhat deranged 

 dm-ing the decay of the fish : the spine has been pressed 

 away from the fin, and is now separated by an inch and a half, 

 or the length of ten or twelve vertebrae. Its exact position 

 might be difficult to determine ; but a comparison with the re- 

 cent dog-fish {Acanthias vulgaris) renders its place tolerably 

 certain. In the dog-fish, as pointed out by Sir P. Egerton, 

 there are one hundred and eight vertebra. Between the head 

 and the first dorsal spine there are twenty-five vertebras ; from 

 the first to the second are included thirty-four ; and beyond the 

 posterior dorsal spine there are forty-nine vertebree to the ex- 

 tremity of the tail. The Falceospinax from the Lias exhibits 

 a remarkable similarity to the recent fish. In the latter there 

 are fifty-nine vertebrae between the head and the posterior 

 dorsal spine, whilst in Palceospinax there are fifty-six ; and 

 from this close relationship it may be infeiTcd with safety that 

 the anterior dorsal spine was situated above the twenty-third 

 or twenty-fourth vertebra. It may be further urged that as 

 there are behind the posterior dorsal spine, in the recent fish, 

 forty-nine vertebra?, there were about the same number in the 

 fossil one : twenty-two are preserved; and a further complement 

 of about six or eight and twenty would complete the caudal 

 portion of the fish. Relative appearances warrant this sup- 

 position. The total length of the fish, including the portion 

 of the snout not preserved, would be 13 inches — a consider- 

 ably smaller example than those described by Sir P. Egerton. 

 The head is represented by the impression of some bones or 

 cartilages not sufficiently well preserved for identification. 

 Tliere are two or three teeth similar in form to the figure no. o, 

 plate vii. of the decade referred to previously, which indicate 

 the proximity of the jaws. 



The spines were deeply implanted in the flesh of the fish, 

 and appear to have had a groove along the back for the re- 

 ception of the fin, though this is only partially evident in my 

 specimen. The anterior spine was smooth, its upper part 

 thickly coated with enamel ; the middle portion of the spine, 

 not actually imbedded in the flesh, was enveloped by the 

 dermal covering of the fish, which was thickly coated with 

 shagreen. The posterior spine exhibits the same characters, 

 except that it was finely, but distinctly, covered with longitu- 



