216 Dr Hibbert on the Limestone of Burdiehouse, 



During the same year (1834) scales of the Megalichthys were shewn to me by 

 W. C. Tkevelyan, Esq. of Wallington, which he had obtained from the coal-fields 

 of Northumberland. 



As these remarks conclude my account of the Megalichthys, I may here mention 

 the information which M. Agassiz communicates to me, that in the much newer 

 formation of Whitby and Scarborough, he has found the fragments of a fish which 

 even exceed in size those of the Burdiehouse animal ; some of the portions of the 

 cranium being nearly two feet in diameter. In announcing to me the discovery of 

 this monster, he adds, " After having seen so many extraordinary and surprising things 

 in the monster of Whitby, which exceeds the largest Ichthyosaurus, I perceive that I 

 am still only commencing the preface of a book, which future years will supply with 

 the wonders of the sea. And I shall think myself happy if I can only have excited 

 interest for a study, which is still so difficult for want of terms of comparison suffi- 

 ciently numerous. 11 



SECTION XIII THE GENUS OF PYGOPTERUS BELONGING TO THE SAUROID 



FAMILY. 



While the primeval waters of the carboniferous epoch had 

 their larger sauroid monsters, they had also lesser sauroid tribu- 

 taries, one of which was in the form of the Pygopterus, belonging 

 to the same family as that to which the Megalichthys has been 

 referred. 



M. Agassiz has favoured me with the following description 

 of the Pygopterus of Burdiehouse. Unfortunately, however, it 

 only applies to a fragment of the fossil fish, which is represented 

 in Plate VII. fig. 2. 



The proportions of the rigid tail of the animal, the relative posi- 

 tion of the dorsal and of the anal fins, the form of the fins, which 

 are horizontally and perpendicularly elongated, as well as the 

 considerable number of rays which compose them, serve to point 

 out the posterior part of a fish of the genus Pygopterus, which 

 belongs to the " Sauroides Heterocerques," (Agass.) Amidst the 

 numerous fragments of bones of the head, as well as of the thoracic 

 cincture, which have been found along with them, it will remain 

 for a detailed description to explain, by the system of exclusions, 

 what might have belonged to the animal. M. Agassiz then 

 conceives, from his having seen so many heads of the Pygopterus, 



