324 C. LAPWORTH ON THE MOFFAT SERIES. 



species of Graptolithina unknown in the earlier zones, but the 

 marked mineralogical characteristics of several of its component beds 

 and their remarkable persistence throughout the district compel us 

 to assign it a special title. 



In the " corrie " at Dobb's Linn the section of the group under 

 consideration, though unfortunately somewhat dislocated, clearly 

 shows a lower division of 15 feet of barren grey rock, and an upper 

 division of 10 feet of black shales and white mudstones. 



In the very centre of the lower division of barren grey shales 

 occurs a double seam of black shale crowded with well-marked 

 fossils, principally : — 



Rastrites hybridus (Lapw.). 

 Monograptus Clingani (Carr.). 



runcinatus (Lapw.). 



- leptotheca (Lapw.). 



Diplograptus folium (His.). 



tamariscus (Nick.). 



Hughesi (Nick.). 



Climacograptus scalaris (His.). 



Monograptus Sedgwicki (Portl.) = spinigerus (Nich.). 



The total thickness of the dark seams on this horizon is about 

 six inches. In the beds immediately in contact with them we meet 

 with laminae reticulated with the trails of Annelides, and dotted 

 with peculiar rounded protuberances. 



The upper division of the zone includes at least six distinct seams 

 of black shale. Some of these are hard and weather into irregular 

 cuboidal pieces. Others are soft, pyritous, and yield beautifully 

 preserved Graptolites. These black flags are divided from each 

 other by thin seams of white mudstone or pale sandy shales. The 

 latter are in several respects the most characteristic strata in the 

 zone. Here they are too greatly shattered and weathered to allow 

 us properly to appreciate their distinctive peculiarities. Elsewhere, 

 however, they are seen to be of a light cream-colour, of a sandy 

 texture, and with a rough harsh surface. Occasionally the latter is 

 cut up into small lozenge-shaped patches by hundreds of fine straight 

 grooves, rarely empty, but almost invariably filled up by quartz or 

 pyrites. 



The fauna of these black shales already recognized by myself at 

 this locality includes the following forms : — 



Rastrites hybridus (Lapw.). 

 Monograptus proteus (Barr.). 



spinigerus (Nich.). 



Hisingeri (Carr.). 



attenuatus (Hopk.). 



interniedius (Carr.). 



Becki (Barr.). 



Diplograptus folium (His.). 



Diplograptus sinuatus (Nich.). 



tamariscus (Nich.). 



Retiolites perlatus (Nich.). 

 Diplograptus Hughesi (Nich.). 

 Dawsonia, sp. 



Discinocaris Browniana (Woodw.). 

 Peltocaris aptychoides (Salt.). 

 Ceratiocaris, sp. ind. 



In the fine section of this zone at the Moory Syke (fig. 9, 

 p. 270), the pale sandy beds are more perfectly exhibited than 

 in the .Dobb's Linn corrie, and there is also a more satis- 

 factory exposure of the dark shale with Monograptus spinigerus, 



