in the Neighbourhood of Edinburgh. 187 



which has not a little contributed to solve some important questions which the osseous 

 relics of the quarry have suggested. 



While Mr Robison was thus rendering the most valuable assistance in the com- 

 mon object which we had in view, this co-operation was the means of affording me 

 the more leisure to satisfy myself regarding other questions of geological interest sug- 

 gested by these researches. 



SECTION VI THE GENERA OF FOSSIL FISH DISCOVERED AT BURDIEHOUSE. 



The fish discovered at Burdiehouse will be described after 

 the system of M. Agassiz, Professor of Natural History at Neu- 

 ch&tel, whose " Recherches sur les Poissons Fossiles," is already 

 familiar to most geologists. They will also be noticed in con- 

 nection with the judgment passed upon them from personal in- 

 spection by this eminent naturalist ; and, in availing myself of 

 the kind assistance which he has thus rendered me, I would con- 

 fess to an obligation for which I am truly grateful. 



M. Agassiz's system, as is well known to those who may have 

 but glanced at his work, while it carefully includes the distinctions 

 which prevail in older recognised systems, gives a characteristic 

 pre-eminence to that portion of the structure of the fish, which 

 with geologists ought to claim a leading consideration. The skin 

 of the fish connects the animal with the medium in which he 

 lives. It is the essential character of the skin to form a sort of 

 external skeleton, which protects its surface. Its epidermis may 

 be considered, in the most general point of view, as a membra- 

 nous layer of horny substance, which covers the whole surface of 

 the animal, which isolates it from the external world, which 

 shelters the more delicate part of its organization, and which, as a 

 bad conductor of heat, preserves to it that degree of internal tem- 

 perature which is essential to its vitality. While this covering is 

 composed of a number of layers, or folia, superimposed upon and 

 strongly adhering to each other, it is at the same time insensible, 

 and is reproduced with ease. — Recherches sur les Poissons Fos- 

 siles, torn. i. p. 26, &c. 



Aa2 



