82 Dr Fleming on the Scales of Vertehrated Animals 



formation, it becomes brownish red, and includes strata of slate 

 clay and conglomerate. On the surface of the strata, in these 

 lower beds, circular spots, some of them nearly a foot in diameter, 

 may be readily perceived by their pale yellow colour, contrasted 

 with the dark red of the surrounding rock. These spots, however, 

 are not, as may at first be supposed, mere superficial films, but 

 derive their circular form from a coloured sphere to which they 

 belong. This sphere is not to be distinguished from the rest of 

 the bed by any difference in mechanical structure, but merely by 

 the absence of much of that oxide of iron with which the other 

 portion of the mass is charged. The circumference of this coloured 

 sphere is usually well defined, and at its centre may always be 

 observed matter of a darker colour, in some cases disposed in 

 concentric layers, in others of calcareous and crystalline matter, 

 the remains, probably, of some vegetable or animal organism, the 

 decomposition of which exercised a limited influence on the 

 colouring matter of the surrounding rock. In some cases, I have 

 observed these spheres slightly compressed at opposite sides, in a 

 direction parallel with the plane of stratification, the result, without 

 doubt, of the subsidence, or contraction of the mass, after the 

 central matter, or nucleus, had ceased to exercise its influence. 



In general, this bed of yellow sandstone is covered directly by 

 the carboniferous limestone ; but, in some instances, as at Wemyss- 

 hall Hill, the bed of greenstone, which usually occurs in the series 

 of the coal metals, considerably above the carboniferous limestone, 

 and forms the summits of the eminences near the extremity of the 

 coal field, overlaps the intervening beds, and comes directly into 

 contact with the yellow sandstone. 



In many parts of this rock, extensive quarries have long furnished 

 excellent materials for building. Some of the seams afford a very 

 durable stone, easily shaped by the chisel, and feebly acted on by 

 the atmosphere. 



At the lowest part of this yellow sandstone, a thin bed of 

 compact limestone occurs, but nowhere, within the county of 

 Fife, of any considerable extent. It may be observed at Craig- 

 foody, in the parish of Dairsie, and at Newton, to the north of 

 Auchtermuchty. It appears to be destitute of organic remains ; 

 and, instead of the black flint which occasionally abounds in the 

 carboniferous limestone, it presents irregular patches of red jasper. 

 It appears to be similar in its character to that which is deno- 

 minated cornstone by several English geologists. This yellow 

 sandstone occupies the bottom of the valley of Stratheden, and a 

 considerable portion of the acclivity of the hills which form its 

 southern boundary, from the Lomonds to St Andrews. 



2. Amygdaloid, 



This rock is less regularly stratified than the sandstone. The 

 strata are thick, and variously curved. The upper portions of this 



