in the Neighbourhood of Edinburgh. 269 



absence of all such remains in the Burdiehouse deposit shews, 

 that its waters were unfavourable to the manifestation of marine 

 mollusca and conchifera. 



%dly, While the comparatively sparing quantity of plants to 

 be found in the limestone of Derbyshire rather indicates that they 

 had been washed into an estuary, or diffused through a sea near 

 the influx of rivers, the immense abundance of plants contained 

 in the Burdiehouse limestone, prove the actual flowing of some 

 river, or fluviatile expanse, through a marshy tract, in which ferns 

 and lycopodiaceae flourished. 



The two foregoing points of difference form the great grounds 

 of distinction between the limestone of Ashford, considered as 

 the deposit of an estuary, and the limestone of Burdiehouse, con- 

 sidered as a pure fresh-water deposit. Other circumstances point 

 to similar grounds of distinction, though perhaps less decisive. 



Sdly, While the limestone of Ashford contains no entomos- 

 traca whatever, they are found in such abundance in the limestone 

 of Burdiehouse, as to occasionally impart to it an oolitic character. 



Now, the presence of these entomostraca can scarcely be con- 

 sidered decisive so long as we know that marine waters can ex- 

 hibit Cythereae, and that the limestone of Burdiehouse encloses 

 many different kinds of entomostraca. The circumstance, how- 

 ever, of the Cypris being found in the Burdiehouse limestone, is 

 assuredly presumptive of this deposit having been formed among 

 the stagnant fresh- waters of ancient marshes. 



4thly, While the Ashford limestone encloses no remains what- 

 ever of such small fish as are abundant in the sandstones, bitu- 

 minous shales, or bands of limestone, which contain plants and 

 fresh-water unios, but in which all marine remains are absent, 

 these fish appear most abundant in the limestone of Burdie T 

 house, presumed to be of fresh-water origin. 



