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 Rosisoy. 
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 nucirorMis, 
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 pcsition. 
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 Sphzenopteris affinis, along with coprolites, and 
7 
