118 Br. R. H. Traqiiair — On the Genus Megalichthys. 



fin of Glyptolepis, but whicli was in reality a portion of the pectoral.^ 

 A specimen from the Coal-measures of Dalkeith, in the Edinburgh 

 Museum of Science and Art, shows also very 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 Diplopterus, 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 3Iegalichthys 

 is, however, the specimens from Burdiehouse, which form the especial 

 subject of the present communication. 



No doubt, in applying the name Megalichthys Bibherti to the 

 specimen at Leeds, Agassiz believed that he had before him the head 

 of the same species, whose rhombic enamelled scales he had pre- 

 viously 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 repre- 

 sented by more than a few detached scales and bones, the entire 

 contour of the fish, the arrangement of the fins and many details 

 regarding 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 dift'erent 

 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 Bhizodus, by Dr. Hibbert 

 in his classical memoir before the publication of Agassiz's 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 Megalichthys 

 Bibberti, 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 allowing it to retain the name 

 which it has borne now for forty years. 



Proceeding now to the description of specimens, the first which 

 may be noticed is one in the Edinburgh Museum (Hugh Miller 

 Coll.), which is pretty entire though small (PI. V. Fig. 1). It 

 measures lOf inches in length, though it must be noted that the rays 

 of the caudal fin are somewhat frayed and broken at their ex- 

 tremities : the greatest depth of the body is If inch ; the length of 

 the badly-preserved head is 2f inches. The pectoral fin is not 

 shown, but all the others are, though perhaps not in so complete a 

 state of preservation as might be wished. There are two dorsal fins, 

 of which the anterior one is the smaller, and commences Gi inches 

 from the front, while the second arises 1^ inch further back. The 

 ventral arises opposite a point rather behind the origin of the first 

 ' Pander, q^. c«Y..p. 68 ; Huxley, q^. c«i;. p. 7. 



