CONODONTS IN AREXIG-LLANDEILO FOPvMATIONS. 241 



Conodoiits; it is pretty inucli crushed, the chert bed here having 

 been folded on itself. However, there was a suflficient quantity 

 of good stuff to have shown Conodonts had they been present 

 in anything like the number they are in the Hunt Law Clench 

 bed and other exposures of the chert-shales. 



I mention these instances to show, as I think, that the 

 Conodonts will be useful as marking zonal bands of the Radio- 

 larian chert-beds of the South of Scotland. 



I need not give a detail of all the examinations I made. I 

 may, however, say that the absence of Conodonts in some 

 instances may have been due to the deformation the beds have 

 undergone from pressure, but I was constantly being astonished 

 to find Conodonts on strongly slickensided surfaces, where one 

 would have expected that such delicate little things would have 

 been brushed away by the differential movement of the rocks. 



The present condition of most of the chert-shales is in a great 

 measure due to weathering or rotting, and, of course, more or less 

 to pressure. The Wanlock Water chert-shales are evidently fresh 

 and solid ; those in Windgatefoot Cleuch are dirty white, blotched 

 with blue; those in Raven Gill are in colour and consistency not 

 unlike gamlx>ge, and break up when placed in water; Bennane 

 Head has green, reddish, and grey shales; head of Shillen Glen, 

 Wanlockhead, dirty yellow; head of Glenkip, Leadhills, cream 

 coloured, and sometimes blotched with a fine red manganese 

 bloom. In the mouth of the little valley between Wellgrain 

 Dod and Wool Law, Leadhills, the shales are soldered to the 

 chert, so that the bed here forms cliffs which break up by 

 weathering into blocks of several feet in size. The shale is, 

 however, so " shorn " that, after being prepared for the micro- 

 scope, it shows few fresh surfaces, the fractures being mostly 

 rusty joints. On the Glengonar slope of Waterhead Hill, near 

 Leadhills, an almost continuous exposure of two hundred and 

 thirty paces across the outcrop of the chert (enclosing a black 

 shale band with flinty ribs) can be seen, and the chert here 

 probably measures twice that thickness — this bed, in this 

 locality, having been often foldetl on itself. The shale is yellow 

 and grey, Conodonts being abundant at parts. The specimens, 

 however, are not well preserved, owing to the folding and crush- 

 ing the strata here have been subjected to. In Normangill 



