(230.0 
On the Constitution of the Ichthyohtes of Stromness. Bs 
ANDREW FLEMING, A.M., M.D. Communicated by the 
Author. 
In the month of August 1840, I enjoyed an opportunity, 
through the kindness of Robert Stevenson, Esq., Civil-En- 
gineer, of visiting Stromness, in Orkney, and the quarries 
which have been opened in the Bituminous Schists of its 
neighbourhood. These schists have acquired considerable 
notoriety from the abundance of organic remains, chiefly be- 
longing to the class of fishes, distributed throughout their 
beds. 
The first attempt to determine the specific differences of 
these organisms was made by Messrs Sedgwick and Mur-- 
chison, in their important paper, ‘“‘ On the Structure and Re- 
lations of the Deposits contained between the Primary Rocks, 
and the Oolitic Series in the North of Scotland,” inserted in 
the Transactions of the Geological Society of London, second 
series, vol. iii, Part I, p. 125. Subsequently, and aided 
by the industry of several collectors, M. Agassiz has been 
able, satisfactorily, to determine the characters of a consi- 
derable number of species, several of which he has figured 
in his invaluable work on Fossil Fishes. My attention hav- 
ing been chiefly directed to the mineral state of the organisms, 
I shall confine the following remarks to this bearing of the 
subject. 
The schists themselves, which include these organic re- 
mains, may be considered as thin slaty sandstones, in which 
the strata vary from a thickness less than a line to upwards 
of a foot. Even in the thickest strata, the facility of split- 
ting into subordinate slabs, indicates the predominance of the 
slaty structure. In the portions where the strata are thickest, 
the rock is coarser, or more arenaceous, than in the thinner 
slaty strata, where the constituent sand is finer, and the clay 
more abundant. ‘The structural character of the whole for- 
mation gives unequivocal indications of its deposition hav- 
ing taken place in comparatively still water, the coarser and 
finer varieties marking the limits of the disturbing causes. 
