92 STRATIGEAPHICAL GEOLOGY 



purple false-bedded quartzitic sandstone containing many grains of 

 glauconite and about 50 feet thick. 



The limestone and associated red shales have yielded several 

 species of Hyolithes and of Orthotheca, with Stenotheca rugosa, 

 Coleoloides typicalis, Kutorgina cingulata and Iphidea labradorica, 

 and Orthisina transversa. The facies of the fauna is that of the 

 Lower Cambrian or Olenellus zone, though no trilobites have yet 

 been found. 



The Shaly Division (Upper Cambrian). In the Malvern 

 area this is over 2000 feet thick, and is divisible into two parts. 

 The lower 800 feet are black shales with bands of basaltic lava 

 which have generally been regarded as contemporaneous lava-flows, 

 but which Dr. Groom finds to be intrusive sills. These shales 

 have yielded Peltura scarabceoides, Gtenopyge bisulcata, Agnostus 

 trisectus, Sphcerophthalmus alatus, etc. species which are character- 

 istic of the Lower Dolgelly Beds of North Wales. The upper part 

 of the Malvern shales is composed of bluish or yellowish -grey 

 shales, with many intrusive sills of basalt and diabase. Dr. 

 Groom 15 found them to be of much greater thickness than was 

 previously supposed, and from his section, reproduced in Fig. 18, 

 it will be seen that they are at least 1300 feet thick. Their 

 highest beds contain Dictyograptus socialis, Agnostus dux, Cheirurus 

 Frederici, Acrotreta Sabrince, with species of Asaphus and Olenus ; 

 most probably they are of Lower Tremadoc age. No representatives 

 of the Menevian, Maentwrog, or Ffestiniog beds have yet been 

 recognised, but the boundary between the Hollybush sandstone 

 and the Malvern shales seems to be a faulted one, so that beds of 

 intermediate age may be faulted out. 



In Shropshire the Shineton shales occupy a tract two miles 

 broad in the valley of the Severn by Shineton and Cressage, and 

 they extend both to the north-east and south-west (see map, Fig. 

 21). They also occur at Pedwardine, and again in a long narrow 

 strip on the west side of the Longmynd, where they underlie 

 the Arenig Beds of the Stiper stones. Their true age was first 

 made known by Dr. Ch. Callaway, 16 who discovered in them fossils 

 of Upper Cambrian types. They are soft, fissile, micaceous shales 

 of a dark - blue colour, weathering to olive - green and yellow. 

 Their base is not seen, and their junction with the Comley 

 sandstone appears to be a fault, so that here, as at Malvern, the 

 central part of the Cambrian System seems to be missing. The 

 lowest beds contain Dictyonema. The highest beds are more 

 fossiliferous and have yielded many trilobites, including Eulonia 

 monile, Olenus Salteri, Asaphellus Homfrayi, A. Crofti, and 

 Shumardia salopiensis, with the Cystidean Macrocystella Marice. 



