﻿524 ME. F. E. C. EEED AND PEOF. S. H. EEYNOLDS ON [K'OV. I908, 



is now carried on. The limestone-bands are, however, generally 

 easilj traceable, either by the ridges to which they give rise or by 

 means of old quarries. 



(a) The Horseshoe-Farm area. — The only sj3ot in the 

 southernmost part of the area where exposures occur is in the 

 neighbourhood of Horseshoe Farm. This lies within the large 

 area shown on the Geological-Survey map as Ludlow, and close to 

 the outcrop of the Old Ked Sandstone. Horseshoe Farm, too, is 

 interesting as being the only spot in the Tortworth Inlier (with the 

 exception of Purton Passage) where Murchison recognized Ludlow 

 rocks. He describes them as follows : — 



' A few beds there [that is, at Horseshoe Farm] contain some of the fossils, 

 particularly Cypricardia [= Orthonota] amygdalina, and pass conformably into 

 the overlying Old Eed Sandstone, and downwards into beds with Asaphus 

 \=Fhacops\ caudatus, etc' (' Silurian System' 1839, p. 455.) 



Partly with the view of clearing up the point as to the occurrence 

 of Ludlow rocks at this locality. Lord Ducie some two years ago 

 had a well suuk in the field to the north of Horseshoe Farm. 

 The material passed through consisted, in the main, of a variable 

 series of greenish sandy and marly beds with a little limestone. 

 The only fossils found were crinoid-stems and a few indeterminable 

 brachiopods. In the lane, however, south-east of the farm there 

 is a good exposure of a variable series of fissile red and yellow 

 sandstones, sometimes micaceous, sometimes calcareous, alternating 

 with bands of hard grit. From these we obtained a considerable 

 suite of fossils (see list, pp. 541-43, which, however, also includes 

 fossils from Lord Ducie's collection), and although the presence of 

 Chonetes striatella, Orbiculoidea rugata, Aviculojpecten Banbyi, and 

 probably Gucullella antiqua, suggests Ludlow beds, the general 

 facies is Wenlock. The strata lie almost horizontally, dipping at 

 an angle of less than 10° south-eastwards, this low dip explaining 

 the great increase in the width of the Wenlock outcrop. 



The Jermyn-Street Museum contains two specimens of Phacojps 

 Weaveri from Horseshoe Farm, which were figured by Salter.^ 

 These are entered as of Ludlow age, and occurring on the 

 same block are examples of RhyncJionella nucula. Salter describes 

 the trilobites as representing a ' larger form of the species ' (Ph. 

 Weaveri) ; and, with regard to the age of the beds, he sa5's that 

 * it is possible there is a boss of May Hill Sandstone at this 

 place.' But the reference of these two specimens to the same 

 species as the typical May-Hill Phacops Weaveri may well be 

 questioned. '-^ The matrix, too, in which the fossils are preserved 

 is unlike anything with which we have met at Horseshoe Farm, and 

 resembles the Wenlock Limestone of the district. 



1 * Monogr. Brit. Trilob.' (Pala'ont. Soc.) 1864, p. 58 & pi. iii, figs. 2-3. 



^ The specimens have recently been minutely re-examined by one of us 

 (F. R. C. E..), and their specific distinction from the May-Hill form is regarded 

 as indubitable 



