190 Dr Hissert on the Limestone of Burdiehouse 
acknowledgments which M. Acasstz pays to the French naturalist for having com- 
mitted to his possession all the materials which the Baron had himself collected with 
a view to similar researches, for which his important occupations in another depart- 
ment, namely, in the extinct land, and amphibious animals of a past state of our 
globe, had afforded him too little leisure. 
A second recommendation of M. Acasstz is, that he comes before us not only in 
the character of a zoologist, but as one who has studied the character of fish in refer- 
ence to their geological connections; who has endeavoured to trace in this class of ani- 
mals the changes of organization which have happened in correspondence with the 
various revolutions which the earth has undergone. “ Fish,” as he observes, ** be- 
ing more than all other animals most intimately connected with the incidents of the 
water, and their organization being besides very high up, they are better calculated 
than any other class to give us clear ideas regarding the changes which have been 
going on in such vast seas as have formerly covered over the earth. We shall be en- 
abled to determine if a fish has lived in rivers, in lakes, or in ponds, in the high sea, 
or upon its shores ;—if it was an inhabitant of the surface of the water or of its 
great depths ;—which indications, more or less valuable, will aid us in determining 
corresponding circumstances with regard to the formation of rocks.” 
If I had space allotted me in this memoir, I could point out many instances of 
the tact which M. Acasstz evinced while in Edinburgh, illustrative of the import- 
ance of fossil ichthyology, in the assistance which it yields in determining the rela- 
tive age of rocks, and which would show, at the same time, how inexcusable I should 
have been if I had not availed myself of a judgment of such value as that which he 
has evinced. 
SECTION VIL—THE FOSSIL FISH REFERABLE TO THE LEPIDOID FAMILY. 
For motives of convenience, I shall not describe the fish which 
I mean to notice in the exact order of classification already ex- 
plained. 
As I have stated, the Lepidoid family is included in the 
Ganoid order of fish. 
To this family the genera of Palzoniscus, Eurynotus, and 
Amblypterus are referred, of which one species or more of each 
have been discovered in the quarry of Burdiehouse. 
The fish which the limestone entombs in far the greater 
number is an individual which I had little difficulty in referring 
to the genus of Palaoniscus. (The first specimens discovered of 
this fish were sketched in Plate VII, figs. 1. and 3. But more 
perfect ones having been subsequently obtained, they are introduced 
