208 Dr Hibbert on the Limestone of Burdiehouse, 



found upon the palatine bones ; but in other species of the same 

 animal, they rather occur upon the margin of the maxillary bone, 

 and more especially in their anterior part. 



And again, in the new genus of Macropoma (Agass.) of 

 which Mr Mantell's Amia Lewesiensis is considered as the 

 type, and of which M. Agassiz professes he is not acquainted 

 with any living species, a similar alternation was observed. Teeth 

 of very different sizes occurred, always smaller on the edge of the 

 jaw bones, and proportionally very large upon the internal bones 

 of the mouth, so that it would have been difficult to conceive 

 that the fragments shewing a series of palatine teeth, or those 

 shewing a series of maxillary teeth, had belonged to the same 

 fish, if they had not been found united in other examples. 



These were the instances of analogy by which M. Agassiz, in 

 the first instance, proposed to explain the difference in the size 

 of the teeth which are distributed along the jaws of the Mega- 

 lichthys, and from which he inferred that a similar disposition 

 might prevail in the Burdiehouse animal. His anticipation, as 

 I have remarked, was singularly confirmed. 



It has been at length shewn that in the Megalichthys very 

 large teeth have coexisted with very small ones ; but as they se- 

 verally exceed so much in magnitude those of the recent Lepi- 

 dosteus, our admiration is greatly excited in contemplating the 

 enormous sauroid fish of a former world. 



The larger teeth of Plate IX. fig. 2 and 10, have a breadth 

 at their base of If to 2 inches, and a length of nearly 4 inches 



After having explained the teeth and their distribution, I now 

 proceed to the scales of the Megalichthys. 



One description of scales exhibits a coating of enamel of a nut- 

 brown colour, and often of the most brilliant lustre imaginable. 

 These scales are of various forms, as may be seen in Plate VIII 

 fig. 3 to 5, and Plate XI. fig. 2 to 8. They are generally angular. 

 A curious character is the punctured surface, which many of these 



