110 ox THE MICEOSCOPIC STETJCTUEE OP THE 



DlSCUSSIO^f. 



The Eev. "W. B. Clarke, Chairman, said that Dr. Barkas had 

 studied the Ctenodus chiefly from the teeth, and had compared 

 these with the teeth of Ceratodus. "When he (Mr. Clarke) first 

 saw the recent Ceradotus he examined the teeth, and pointed out 

 to the Curator of the Museum that it was a Ceratodus, referring 

 him to the plates in the Poissons Fossiles of Agassiz. Sir C. "W. 

 Thomson had also shown him fossil teeth of Ceratodus found 

 embedded in the soil of Queensland. In the Geological Maga- 

 zine for 1869 the father of Dr. Barkas had described the teeth 

 of various species of Ctenodus found in the Coal Measures of 

 Northumberland, and of some of these teeth figures were given 

 as shown in the Magazine, vol. YI, produced. 



There was a difierence between Ctenodus and Ceratodus, yet 

 they were related. It was a marvellous fact that a fish of such 

 antiquity in Europe as Ceratodus should be found living at the 

 antipodes. Mr. Clarke then exhibited to the meeting teeth of 

 Ceratodus of several species from Wurtemburg. 



Part II. 



ON THE MICROSCOPIC STRUCTURE OE THE MAN- 

 DIBULAR AND PALATAL TEETH OP CTENODUS. 



By W. J. Baekas, M.E.C.S.E., L.E.C.P.L. 



lEead lefore the Boyal Society of KS.W., 4 October, 1876.] 



In my last paper I described the external characters of the 

 teeth of all the species of this genus that have been discovered, 

 and hinted at the classification and probable distribution. To- 

 night I shall draw your attention to the minute structure of the 

 teeth, and as I find from my investigations that they possess a 

 similar structure in all the species, I shall take C. tuherculatus, 

 this species possessing the largest teeth and being the most 

 common, as a typical tooth. G. eleqans apparently diff'ers in 

 structure but in reality it does not do so, as I shall show in the 

 course of my remarks. 



Professor Agassiz, while describing the difierent species in his 

 " Poissons Eos^iles" that were known to him at the time of publi- 

 cation of that great work, refers to the structure of C Bohertsoni 

 only, leaving it to be conjectured that it was the only species he 



