in the Neighbourhood of Edinburgh. 245 



Burdiehouse, along with coprolites, shewing that they are them- 

 selves a portion of the lacustrine deposit of this locality. 



In the uppermost bed of argillaceous shale, specimens of the 

 Unio have lately been discovered by the quarrymen, which were 

 placed in my hands by Mr Robison. 



In the annexed wood-cut, the natural size of the bivalve is 

 represented, though some specimens occur a little larger. It 



does not appear to me that this 

 species has yet been described. It 

 differs from any unio which I have 

 yet seen represented in the tumi- 

 dity of its form, which is rounded into a sort of nut-shape. The 

 shell is much less elongated than the Unio Urei, which holds a 

 similar lace in the carboniferous group of Scotland. If it should 

 prove a new species, which I suspect, I propose to call it, in refe- 

 rence to its shape, the Unio nuciformis. 



I have at length enumerated the beds which may be account- 

 ed as inferior to the limestone of Burdiehouse, and I have also 

 glanced at contiguous strata holding a superincumbent position. 

 Their line of direction is from SS.W. to NN.E. The dip is 23° 

 to 25° SE. 



Owing to the covered state of the ground, Burdiehouse is the 

 only locality where this limestone is seen to crop out. The pre- 

 vailing notion is, that it reappears at the foot of the Pent- 

 lands, and that, at Carlops, it is to be identified with a seam of 

 limestone not more than six inches thick. But this is a very 

 doubtful opinion. 



Another circumstance to be remarked is, that there is no evi- 

 dence of the deposit being a continuous one. Thus, in the excel- 

 lent manifestation of strata which may be traced from the vicinity 

 of Siccar Point in Berwickshire to Cove, this fresh- water limestone 

 is deficient. But, in the place of it, there appears to be a bed of 

 bituminous shale, in which I detected the characteristic fern of 

 Burdiehouse, the Sphaenopteris affinis, along with coprolites, and 



7 



