Geological Society. 229 



III. Lower Ludlow Rock. — Equivalent, " Die Earth." 



This group is chiefly made up of incoherent, grayish, argillaceous 

 schist, seldom micaceous. The higher strata are in some places 

 charged with many Orthocerata of new and undescribed species, 

 Lituites, Asaphus caudatus, &c. Other beds are locally distinguished 

 by concretions of argillaceous limestone, formed around corals and 

 other organic bodies ; and towards the base of this deposit a thin 

 calcareous zone is observable in Shropshire, containing the Penta- 

 merus Icevis and a new species of that bivalve, both differing from the 

 species noted in the overlying group 2. The thickness is supposed 

 to exceed 2000 feet. 



The dislocations and faults on the Severn are described, by which 

 this unproductive shale or "Die Earth" is brought in one point into 

 unconformable contact with, and in another passes conformably be- 

 neath, the coal fields of Madeley and Brosely. 



IV. Shelly Sandstones. — Equivalent, — — ? 



Red and green colours predominate in these sandstones, although 

 purple and white are also frequently observed ; by which charac- 

 ters, as well as by the nature of the stone and the specific differences 

 in the organic remains, this formation is clearly distinguished from 

 any of the overlying groups. Associated with the sandy strata are 

 calcareous bands, almost made up of Productae, Leptaenae, and Spi- 

 riferi, with crinoidal remains, all differing from those in the superior 

 deposits. In Shropshire this formation rises at low angles from the 

 valleys of lower Ludlow rock or Die Earth, and occupies separate 

 ridges on the south-eastern flanks of the Wrekin and the Caer Cara- 

 doc. By a rough estimate 1500 to 1800 feet are assigned to the 

 depth of the deposit. 



V. "Black Trilobite Flagstone" #c— Equivalent, ? 



The prevailing Trilobite in this formation is the large Asaphus 



Buchii, which with the other associated species is never seen in 

 any of the overlying groups. In the mountain called the Long- 

 mynd, this flagstone is made up of black schists, hard and dark- 

 coloured grauwacke sandstone, &c., in which Trilobites have not 

 yet been observed, although they are abundantly characteristic of 

 the same zone in its prolongation through Radnor, Brecknock, and 

 Caermarthen shires, where these fossils occur in black limestone and 

 calcareous flagstone and grit. The thickness of this formation pro- 

 bably exceeds that of any one of the superior groups. 



VI. Red Conglomerate, Sandstone, and Slaty Schist. 



This is a vast deposit of several thousand feet in thickness, con- 

 sisting of very coarse, quartzose conglomerates, which alternate with 

 some schistose beds and much purple-coloured sandstone (Com- 

 pound Sandstone of Townson), the strata of which in Haughmond, 

 Pulverbatch, and Linley Hills, Shropshire, are highly inclined or 

 vertical, in conformity with those of the preceding formation. No 

 organic remains have been observed, by which, and by its very pe- 

 culiar mineral structure, this formation is shown to be entirely distinct 

 from the preceding groups. 



