306 C. LAPWOKTH ON THE MOPPAT SERIES-. 



shattery mudstone is visible, apparently overlying them, but possibly 

 of earlier date. 



Between the two black-shale exposures lie the grey- and orange- 

 coloured mudstones with ribs of flagstone, so conspicuous iu the 

 Craigmichan and Berrybush sections. They are, however, too much 

 faulted and contorted to allow us to determine with certainty their 

 precise relationship to the foregoing beds, or to those of the more 

 receut Hartfell Shales. 



The small sections of Glenkiln Shales visible at Belcraig have 

 already been sufficiently described. That in the main stream shows 

 only the dark shales ; in the side stream many of the pale mudstones 

 are apparent (fig. 18, p. 284). 



In the main cliff at Dobb's Linn, 12 feet of the fossiliferous por- 

 tion of the Glenkiln Shales are exposed. Fossils are not uncom- 

 mon, but are generally in a very indifferent state of preservation. 



Fossils from the Glenkiln Shales of Dobb's Linn. 



Dicellograptus Forchhammeri (Gein.). J Diplograptus angustifolius {Hall). 



Didyuiograptus superstes (Lapw.). •? bimucrouatus (Nick.). 



Dicranograptus ziczae (Lapw.). Olimacograptus bicornis (Hall). 



Mcholsoni (HopJc.). j ' , var. peltifer (Lapw.). 



Diplograptus fbliaceus (Murch.). I perexcavatus (Lapw.). 



tricornis (Carr.). I Tkamnograptus typus (Hall). 



Lithologically, the unfossiliferous portions of the Glenkiln Shales 

 and the superior subgroup of barren mudstones of the overlying 

 Hartfell division are very similar in their general features ; and it 

 occasionally happens that when the two are seen in juxtaposition it is 

 almost impossible to distinguish them. This is not the case, how- 

 ever, where the intercalated flagstone ribs are present, as these are 

 wanting from all except the very lowest Hartfell Shales. There is 

 a corresponding resemblance in the carbonaceous beds of the two 

 divisions, both consisting of hard black slaty shales and thin-bedded 



On the other hand the zoological features of the Glenkiln Shale 

 are strikingly distinct. Its fauna is characterized by the exclusive 

 presence of such conspicuous genera as Coenograptus, Didymograptus, 

 and Thamnograptus, none of which have hitherto been recognized in 

 strata of later age. Even the genera common to its lower beds and 

 those of the Hartfell Shales are represented in the two formations 

 by species totally distinct. The most prevalent of the peculiar Glen- 

 kiln species belonging to these common genera are Dicellograptus 

 divaricates (Hall), D. sextans (Hall), Dicranograptus formosus 

 (Hopk.), D. ziczae (Lapw.), Diplograptus Whitfieldi (Hall), D. den- 

 tatus (Brongn.), Olimacograptus ccelatus (Lapw.), &c. 



§ II. The Hartfell Shales. 



The second or Hartfell division of the Moffat Scries attains a 

 thickness of about 100 feet in the typical sections of the Moffat 



