THE OLD RED SANDSTONE. 167 
and conglomerate belt in which these orgznisms occur, there 
rests, as has been said, a band of limestone, and over the 
limestone a thick bed of yellow sandstone, in which the sys- 
tem terminates, and which is overlaid in turn by the lower 
beds of the carboniferous group. 
The limestone band is unfossiliferous, and resembling, in 
mineralogical character, the Cornstones of England and 
Wales, it has been described as the Cornstone of Scotland; 
but the fact merely furnishes one illustration of many, of the 
inadequacy of a mineralogical nomenclature for the purposes 
of the geologist. In the neighborhood of Cromarty the lower 
formation abounds in beds of nodular limestone, identical in 
appearance with the Cornstone;— in England similar beds 
occur so abundantly in the middle formation, thur it derives 
its name from them ;—in Fife they occur in the upper 
formation exclusively. ‘Thus the formation of the Coccosteus 
and Dipterus is a cornstone formation in the first locality ; 
that of the Cephalaspis and the gigantic lobster in the second ; 
that of the Holoptychius nobilissimus in the third. We 
have but to vary our field of observation to find all the for- 
mations of the system Cornstone formations in turn. The 
limestone band of the upper member presents exactly similar 
appearances in Moray as in Fife. It is in both of a yellowish 
green or gray color, and a concretionary structure, consisting 
of softer and harder portions, that yield so unequally to the 
weather, as to exhibit in exposed cliffs and boulders a brecci- 
ated aspect, as if it had been a mechanical, not a chemical 
deposit ; though its origin must unquestionably have been 
chemical. It contains minute crystais of galena, and abounds 
mw masses of a cherty, siliceous substance that strikes 
fire with steel, and which, from the manner in which they 
are incorporated with the rock, show that they must have been 
