270 Dr Hibbert on the Limestone of Burdiehouse 



This circumstance, also, considered as an argument, is not 

 free from ambiguity. Although I conceive that, during the car- 

 boniferous epoch, smaller fish dwelt more in fresh- water lakes or 

 rivers, whither they were pursued by larger finny monsters, I 

 should be sorry to affirm that they might not frequent estuaries, 

 or arms of the sea. One genus of Palaeoniscus is found in the 

 limestone of Burdiehouse, and another in the later formation of the 

 magnesian limestone, — which last, I presume, is of marine origin. 



5thly, Remains of fish referable to the family of the Cestra- 

 ciontes (Agass.), appear both in the estuarian deposit of Ashford, 

 and in the fluviatile deposit of Burdiehouse. Now, the appear- 

 ance of these large finny monsters in each formation, at least 

 countenances the opinion which I have advanced, that estuaries, 

 as well as fresh-water lakes or rivers, were visited by them in 

 quest of their prey. 



At the same time, the genera of Cestraciontes found at Ash- 

 ford and at Burdiehouse, are not the same. During the spring 

 of the present year, I procured large bony rays, as well as large 

 palatine and maxillary teeth, from the limestone of Ashford ; but 

 the bony rays widely differed from the character of such as have 

 been referred to the Gyracanthus formosus of Burdiehouse. 



6thly, While the limestone of Burdiehouse enclose s remains 

 of the immense and scaly Megalichthys, it is only a probable con- 

 jecture that similar relics might have been discovered at Ash- 

 ford. (See the Notes to Section XII. of Part. I.) 



It follows from these premises, that, while a limestone which 

 contains marine mollusca, &c. and, along with these remains, the 

 plants common to coal-fields, together with the entomostraca of 

 marshes, may be regarded as an estuarian limestone, other cir- 

 cumstances, although they may point to the same conclusion, are 

 either less decisive, or ambiguous. 



