72 Proceedings of the Boyal Physical Society. 



clearly the obtuse scaly central lobe with its fringe of fin 

 rays. 



As regards the other fins, their number and position are 

 clearly shown in a specimen from the coal-measures of 

 Airdrie, Lanarkshire, in the British Museum. There are two 

 posteriorly situated dorsal fins, which are placed as in Diplo- 

 pteriis, the first opposite the ventrals, the second very nearly 

 opposite the anal. Part of the caudal is shown, but it is 

 unfortunately not in a very perfect condition. 



The best display which I have seen of the fins of Megcd- 

 ichthys is, however, in the specimens from Burdiehouse, which 

 form the special subject of the present communication. 



No doubt, in applying the name Megalichthys HiVberti to 

 the specimen at Leeds, Agassiz believed that he had before 

 him the head of the same species, whose rhombic enamelled 

 scales he had previously seen from Burdiehouse at the 

 Edinburgh meeting of the British Association : there was 

 not indeed material at the time for deciding otherwise. But 

 the Burdiehouse Megalichthys is now represented by more 

 than a few detached scales and bones, the entire contour of 

 the fish, the arrangement of the fins, and many details regard- 

 ing the head being displayed in specimens in the Edinburgh 

 Museum and in other collections. Now, there are certain 

 points which satisfy me pretty fully that the Burdiehouse 

 fish is diiferent specifically from the common coal-measure 

 form of which the head at Leeds is the type, and it might 

 indeed be disputed whether the former has not a prior claim 

 to the specific name " Hihherti^' especially as some of its 

 scales and bones were actually figured under that name, along 

 with remains of Ehizodus, by Dr Hibbert in his classical 

 memoir, before the publication of Agassiz' account of the latter 

 in the " Poissons Fossiles." But the fact that Agassiz, the 

 founder of the genus and species, definitely adopted the Leeds 

 specimen as the type of the first scientific description of Megal- 

 ichthys Hihherti, coupled with the natural feeling that, except 

 on really imperative grounds, it is not wise to disturb long 

 established names, is, I think, sufficient justification for allow- 

 ing it to retain the name which it has borne now for forty years. 

 Proceeding now to the description of specimens, the first 



