316 C LAPW0BTH ON THE MOFFAT SEEIES. 



ciated black fossiliferous shales, and lead insensibly into the thick 

 overlying mass of pale mndstones constituting the Upper Hartfell 

 Group. As a whole the beds of the group are totally barren of 

 fossils^ which are met with only along two widely separated horizons. 

 Here, however, they occur in abundance, and the facies of the fauna 

 thus indicated compels us to assign the containing beds to the same 

 general division as the underlying mass of dark shales. 



The most intelligible section of the beds of this subdivision is 

 exhibited in the Main Cliff at Dobb's Linn and in the gully below 

 the faUs (fig. 28). 



i. Barren Mudstones. — The inferior portion of the Upper Hart- 

 fell consists here of about 30 feet of light-coloured shales and mud- 

 stones. In the lower half of the zone they are arranged in beds 

 of from 6 inches to a foot in thickness ; above they form a homo- 

 geneous mass of shaly rock with few traces of stratification. The 

 inferior beds weather into slabs of a deep rusty-brown colour ; 

 the higher beds into flakes or angular splinters of a light yellow 

 tint. 



No fossils are present in any of its beds, except in a thin seam of 

 black shale, about 2 inches in thickness, not far removed from the 

 base of the zone. This swarms with poorly preserved Graptolites, 

 chiefly Dicellograptus Forchliammeri (Geinitz), Climacograptus sca- 

 laris'? (His.), Diplograptus truncatus (Lapw.). 



The same fossiliferous seam can be recognized in the section at 

 the Moory Syke (fig. 9) ; and there is even a trace of it in the 

 magnificent section of Craigmichan Scaurs. 



Intercalated among these " Barren Mudstones " occur several thin 

 courses or ribs of hard compact rock, slightly calcareous, weathering 

 exteriorly of a deep drab or dark brown colour. They have been 

 recognized only in the section at Dobb's Linn. 



At Craigmichan the lower and thick-bedded portion is very con- 

 spicuous, and the whole zone has expanded to a total thickness of 

 50 feet ; but this may include the representative of the succeeding 

 zone, which is not individually recognizable in the section at that 

 locality. 



Nowhere are the Barren Mudstones so conspicuously exhibited as 

 in Belcraig Burn, where they occupy the greater part of the 

 exposure, and display their peculiar characteristics to perfection. 



These beds also occur along the Ettrick River at Berrybush and 

 at Hartfell Spa, everywhere under the same general aspect, and 

 everywhere totally barren of fossils. 



ii. Zone o/Dicellograptus anceps(iW<$.).— At Dobb's Linn the thick 

 mass of the " Barren Mudstones " is surmounted by a thinner group 

 of somewhat similar beds, diversified by seams of black fossiliferous 

 shales and variegated mudstones. The higher division of this over- 

 lying group is formed of 6 feet of greenish-grey flaggy shale, non- 

 fossiliferous, and identical in all respects with the typical beds of the 

 '• Barren Mudstone." The lower division, which is also about 6 feet 

 in thickness, contains five or six thin seams of carbonaceous shale, 

 soft, fossiliferous, and interbedded with numerous lines of grey, 



