234 MR. L. D. STAMP OX THE HIGHEST [vol. lxxiv, 



The Downton Sandstone itself is not very fossiliferous ; but in 

 its lower part certain whitish bands occur, the colour of which is 

 due to fragments of the delicate valves of Ling til a minima. 

 Complete specimens are rare, and, when complete, the specimen is 

 seen to be a small and stunted form. 



In a few localities the lower part of the sandstone also includes 

 narrow bands full of the casts of HeUeroplion trilobatus. Platy- 

 scliisma and HoJopella occur sparingly through the whole mass of 

 the sandstone. These are sufficient to demonstrate the Silurian 

 age of the rocks. 



Some doubt seems to exist as to the identity of the species of 

 Holopella from this horizon. Murchison l figures H. conica, 

 H. gregaria, and H. obsoleta from the ' Upper Ludlow — -Tilestone 

 Beds. 1 The specimens that I have obtained are too crushed to 

 allow of detailed examination ; but they compare best with 

 H. gregaria or H. conica, since H. obsoleta is a larger species 

 with tumid whorls. Miss G. L. Elles & Miss I. L. Slater 2 

 record II gregaria from this horizon ; but Prof. T. T. Groom 3 

 in the Malvern district records only H. obsoleta from the Upper 

 Ludlow and H. gregaria from the May-Hill Sandstone. 



Several factors necessitate the linking of the grey Platyscliisma 

 Shales with the sandstone of the Downton-Castle Sandstone Series 

 or zone of Lingula minima. There is, first, palteontologieal 

 evidence in the occurrence of 1*1 at y sell is ma and Lingula minima 

 throughout ; secondly, there is the gradual lithological transition ; 

 and, finally, the evidence of the corresponding beds at Downton 

 itself. 



F. Temeside Shales. — The Temeside Shales are the most 

 clearly-differentiated group of rocks in the district, and their lower 

 limit is almost the only sharply-marked division-plane in the whole 

 succession. Throughout their thickness, the prevalent colour of 

 these rocks is olive-green, and they weather to form a very 

 characteristic brick -red soil. 



In the east of the area the lowest beds are rubbly green shales 

 (designated ' marls ' on the Geological Survey map) which rest upon 

 the Downton-Castle Sandstone. The junction is seen in a small 

 quarry along the Bucknell and Weston Road : only a few feet of 

 Temeside Shales are exposed ; but higher beds, consisting of green 

 micaceous sandstone and hard compact green rock, are exposed in 

 the river-cliff close by the railway"- bridge on the same road. 

 Similar beds are seen in the lane from Bucknell Village to Bucknell 

 Hill. 



In the west at Five Turnings, Downton-Castle tilestones are 

 succeeded by micaceous greenish grit, somewhat irregularly bedded, 

 and about 2 feet thick. This grit seems to be extremely variable 



1 ' Silurua ' 4th ed. (1867) pi. xxxiv. 



2 Q. J. G. S. vol. lxii (1906) p. 219. 

 8 ' Geology in the Field ' Jubilee vol. Geol. Assoc. (1910) pp. 713-14. 



