138 THE OLD RED SANDSTONE. 
cast of its roddings, those of the Diplacanthus of the Lower 
Old Red Sandstone described in pages 84 and 85 of the 
present volume, and figured in Plate VIII., fig. 2, except that 
it was proportionally stouter, and traversed at its base by 
lines running counter to the strize that furrow it longitudinally. 
Of the other organisms of Balruddery I cannot pretend to 
speak with any degree of certainty. Some of them seem to 
have belonged to the Radiata; some are of so doubtful a 
character that it can scarce be determined whether they took 
their place among the forms of the vegetable or animal king- 
doms. One organism in particular, which was at first deemed 
the jointed stem of some plant resembling a calamite of the 
Coal Measures, was found by Agassiz to be the slender limb 
of acrustacean. A minute description of this interesting de- 
posit, with illustrative prints, would be of importance to sci- 
ence: it would serve to fill a gap in the scale. The geologi- 
cal pathway, which leads upwards to the present time from 
those ancient formations in which organic existence first 
began, has been the work of well nigh as many hands as 
some of our longer railroads: each contractor has taken his 
part; very extended parts have fallen to the share of some, 
and admirably have they executed them ; but the pathway is 
not yet complete, and the completion of a highly curious 
portion of it awaits the further labors of Mr. Webster, of 
Balruddery. 
A considerable portion of the rocks of this middle forma- 
tion in Scotland are of a bluish-gray color: in Balruddery, 
they resemble the mudstones of the Silurian System ; they 
form at Carmylie the fissile, bluish-gray pavement, so well 
known in commerce as the pavement of Arbroath; they 
occur as a hard, micaceous building-stone in some parts of 
Fifeshire ; in others they exist as beds of friable, stratified 
