Notes on Carhonifei-ous Selachii. 413 



There are two exceedingly well-marked species of common 

 occurrence in the British and Irish Carboniferous Limestone, 

 namely C. mirahilis, Ag., and C. striatus, Ag. C. marginatus, 

 Ag., I also believe to be a good species, as well as G. Milleri, 

 Ag. On C. acutus, Ag., conicus, Ag., hasalis, Ag., Hibherti, Ag., 

 and parvus, Ag., I offer no opinion, not having seen the 

 types ; but as to the new species added by Mr J. W. Davis 

 in his large work on the fossil fishes of the Carboniferous 

 Limestone series of Great Britain,"^ there is scarcel}^ one which 

 will stand the test of careful comparison with the common 

 species described by Agassiz. C. Hornei, Dav., C. elongatus, 

 Dav., and 0. curtus, Dav., are in my opinion simply syno- 

 nyms of C. striatus, Ag.; — C. mucronatus, Dav., and destructor 

 Dav., of C. mirahilis, Ag. It is rather difficult to give any 

 opinion upon C. curvus, Davis. 



In the Edinburgh Museum, and in the collection of the 

 Geological Survey of Scotland, there are a few teeth of what 

 is evidently a new species of Cladoclus from the Lower Car- 

 boniferous rocks of Eskdale in Dumfriesshire, though I 

 refrain on the present occasion from giving it a name. In 

 these teeth the surface of the cones is perfectly smooth 

 and glossy, and in the absence of striations they approach 

 C. van Hornei and prenuntius of St John and Worthen, The 

 thought has struck me, — is it possible that this undoubted 

 Cladodus may represent the dentition of Ctenacanthus costel- 

 latus, the unique specimen of which, with the spines in 

 situ, occurred in the same beds ? It will be recollected that 

 the only tooth visible in the specimen of Ctenacanthus costel- 

 latus was an imperfect one, but its one visible cusp was 

 smooth. If there is any connection here, the specimen of 

 Ctenacanthus costellatus must have been a young individual, 

 as these teeth indicate a fish of much larger size. 



This brings up once more the question of the correlation 

 of Cladodus and Ctenacanthus, a question which I must 

 admit is still involved in great obscurity. When I wrote 

 my description of Ctenacanthus costellatus^ I was inclined to 

 believe that Ctenacanthus and Cladodus represented the 

 spines and teeth of the same genus, and that the genus 



1 Trans. Roy. Dub. Soc, 1883. ^ q^^i^ -^^^^ j^u. i884, pp. 3-8. 



