and around the Warivickshire Coal-field. 549 



in the Menevian of South Wales (Mem. Geol. Surv. vol. iii. p. 472). 

 Dictyonema sociale, Salt, is found in the uppermost Lingula Flags in 

 North Wales (ib. p. 536), in the Shineton Shales (Tremadoc) in 

 Shropshire, and at Malvern (Quart. Journ. Geol. Soc. vol. xxxiii.). 

 Agnostus princeps, Salt., occurs in the Upper Lingula Flags, and 

 Tremadoc Slate of North Wales, and in the Lingula Flags of South 

 Wales (Mem. Geol. Surv. vol. iii. p. 489), and Olenus Salteri, Call., is 

 common in the Shineton Shales of South Shropshire (Quart. Journ. 

 Geol. Soc. vol. xxxiii. p. 666). Lingula lepis, Salt., ranges from the 

 Lower Lingula Flags to the Arenig (Mem. Geol. Surv. vol. iii. p. 538), 

 but is commonest in the Tremadoc. Lingulella Nicholsoni, Call., and 

 Obollela Sabrince, Call., are common in the Shineton Shales (Quart. 

 Journ. Geol. Soc. vol. xxxiii.). 



In Professor Lapworth's list we find the following additional 

 forms : Obolella sagittalis, Salt., which occurs in the Menevian of 

 North and South Wales; 0. Salteri, Holl, known in the Upper 

 Lingula Beds of Malvern ; Orihis lenticularis, Wahl., which occurs 

 in the Upper Lingula Flags (Dolgelly group of Belt); Lingulella 

 pygmea, Salt., of the Upper Lingula Flags ; Serpulites fistula, Holl, from 

 the same beds near Malvern; Sphceroplithalmus (Olenus) alatus, Boeck, 

 of the Upper Lingula Flags, and the black shales of Malvern ; S. 

 flagellifer, Angelin, which occurs in the Lingula Flags, and is 

 believed to range up into the Tremadoc. 



It may be concluded that the Stockingford Shales belong to a late 

 Lingula Flag age, including possibly a portion of the Lower Tremadoc 

 series. 



The base of the Coal-measures. 



The most southerly point at which the position of the base of the 

 Coal-measures has been definitely fixed is the colliery at Hawkesbury 

 Basin, previously alluded to. There the Silurian rocks (presumably) 

 were entered at a depth of 115 feet 5 inches below the Bench Coal, the 

 lowest seam worked in this coal-field. We next find evidence of its 

 position in the railway-cutting near Griff Hollow, as has been described. 

 But in the cutting at Chilvers Coton the junction is fully exposed to 

 view. A coal-seam is seen on the west side of the cutting 116 yards 

 north of the Accommodation Bridge (the second bridge south of 

 Chilvers Coton). This seam is underlain by three feet of white 

 fireclay, which rests upon about eight inches of sandstone. On 

 clearing the soil from the base of this sandstone, it may be seen that 

 it rests upon soft blue laminated shale, weathering yellow, and 

 obviously forming part of the same set of shales in which the 

 intruded diorites described above occur. The dip of the Coal- 

 measures is nearly in the same direction as that of the shales, but 

 is less rapid, so that by clearing a sufficient length of junction it 

 may be seen that there is an actual unconformity. The Coal- 

 measures occupy the cutting to a distance of 130 yards south of the 

 Accommodation Bridge, where the Lower Silurian shales are brought 

 up again by a small fault running about S. 35° E., the evidence for 

 the fault being the fact that the dip of the Coal-measures continues 



