CONODONTS IN ARENIG-LLANDEILO FORMATIONS. 237 



of it is kept bare by the waves. In my examination of the 

 specimens carrie^l off I found no Conodonts. 



At FardingmuUoch, four miles south-east of Sanquhar, there 

 is a good, although partial, exposure of red Arenig shale, and 

 in some of the specimens I selected for microscopic examina- 

 tion I found abundance of Conodonts. This induced me to 

 make a re-exaraination of the Morroch Bay red shale, and for 

 this purpose I collected samples from every foot of the shales 

 — ^sixtj'-six in all. In thisS large examination I only procured 

 some live Conodonts — four of them having been got at the 

 thirty-fourth foot from the south side of the bed. The red 

 shales here are in a vertical position and in excellent presei-va- 

 tion for examining microscopically, splitting easily into thin 

 laminte.* 



The abundance of Conodonts in parts at least of the Farding- 

 muUoch bed, and their extreme rarity in the Morroch Bay one, 

 raises the qu&stion, Do the exposures at these two localities 

 belong to the same period of deposition? In such " fankled " 

 strata as the Silurian Uplands display, this is a question that 

 cannot with any degree of confidence be answered. The best 

 that can be done in the circumstances is simply to say that at 

 both places graptolite shale of undoubted Llandeilo Age occure 

 not far from the red beds. 



The third and fourth exceptions are the thick beds of pale- 

 green Arenig shale which occur close on each side of the retl 

 shales already mentioned. From the lower bed I obtained a 

 few Conodonts, from the upper one I did not get any; but the 

 comparison is not a fair one, as in nearly all the samples — 

 twenty-eight in number — I examined, the shales of the laiter 

 were very much slickensided by crushing, very few of the layers 

 having escaped. 



These Arenig shales, both red and green, are extremely fine- 

 grained, mica being seldom seen in them, and where present 

 on the slickensides it has evidently been developed by earth 

 movements. 



Besides Conodonts, these shales contain hingeless Brachiopods 

 — at least the first one — Foraminifera, Sponge remains ; Kadio- 



* These Arenig shales are sometimes called " mudstones," but I don't 

 see the propriety of this term as applied to them. 



B 



