C. LAP WORTH ON THE MOEPAT SERTES. 303 



sometimes 6 feet in depth. Occasionally argillaceous, they are more 

 frequently highly siliceous, and break under the hammer with a 

 conchoidal fracture. Barely, indeed, do they show any clear evi- 

 dence of internal lamination, but ultimately break up under the 

 influence of the weather into large cuboidal fragments. Prom their 

 intractable character, especially when slightly metamorphosed, they 

 form conspicuous " ribs," or projecting bands, rising above and pro- 

 tecting the easily weathered surfaces of the soft shales in which 

 they are imbedded. They are rarely absent in any of the sections 

 of the Glenkiln Shales of the Moffat area, but nowhere are they so 

 conspicuous as in the Craigmichan exposure, where they run along 

 the basal portions of the cliff to the north of Selcoth Burn for a dis- 

 tance of nearly half a mile. 



In the same section, apparently below the 4t ribbed shale" group, 

 we observe two distinct seams of black shales, which, with certain 

 white or very pale-coloured mudstones and flaggy beds, occupy the 

 central portions of the exposure. The higher black band is 6 feet 

 in thickness, consisting of hard ringing laminae of carbonaceous 

 shales, some of the softer faces of which show Diplograptus tricornis 

 (Carr.), B. foliaceus (Murch.), D. perexcavatus (Lapw.), Bicello- 

 graptus divaricatus (Hall), Climacog raptus ccelatus (Lapw.), 0. Scha- 

 renbergi (Lapw.), an assemblage of fossils very similar in its main 

 features to that afforded by the lowest (Olimacograptus-Wilsoui) 

 zone of the Hartfell division. 



Few traces of this relationship, however, are exhibited by the 

 second and southerly black band. This is similar to the foregoing 

 in mineralogical character, but appears to be 14 or 15 feet in thick- 

 ness. It yields fossils only in one small seam near its summit ; 

 these include: — 



Fossils from the First Glenkiln Band of Craigmichan Scaurs. 



Thanmograptus typus (Hall). 

 Dieellograptus Forchhammeri ( Gein.), 

 Dicranograptus ziczac (Lapw.). 

 Diplograptus foliaceus (Murch.). 

 angustifolius (Hall). 



Climacograptus perexcavatus (Lapw.). 



caslatus (Lapw.). 



Scharenbergi (Lapw.). 



Glossograptus, sp. 



At Berrybush several distinct sections show a similar thickness of 

 concretionary and shattered mudstones and shales, with intercalated 

 ribs of hard sandstone, in corresponding relationship to soft pale- 

 coloured mudstones with thick seams of black shale (fig. 26). 



In the eastermost of these sections, 57 feet of these barren beds 

 are seen, here, however, distinctly dipping below the dark shales at 

 an angle of 45°. They are softer and in every way less altered than 

 in the former locality, weathering of a pale orange-colour. It is 

 impossible to identify the dark shales ; but, as will be seen from a 

 comparison of the sections given, there can be no doubt of the 

 equivalency of the ribbed mudstone groups. If, however, the dark 

 shales are actually the higher beds, the section must be inverted 

 with respect to that of Craigmichan. In the mudstones the burrows 



