D 



332 JURASSIC. 



f^. Trigoiiia-htds, 28 feet. Gritty and shelly limestones, well seen 



in ledges on foreshore south of Bencliff, Weymouth, and 



near Osmington, where there is a pavement of rock 



crowded with specimens of Trigonia clavcUata (also T. moni- 



lifcrd). Nerinica-\)<id.\\\\\\ N. C^Jt'^/Z/tf//// near Weymouth. 



Osmington Oolite, 22 feet. Fine-grained (occasionally pisolitic) 



oolites and oolitic marls, well shown under Bencliff, at 



Wyke, and Osmington. 



Bencliff Grit series, 20 feet. Calcareous grit, sand, and 



laminated sandy clays, with ' doggers ' of indurated calcareous 



sandstone, Bencliff and Osmington. Few fossils. 



B. 2. Nothe Clays, 40 feet. Weymouth Bay. G?ypliira dilaiata, etc. 



. f I. Nothe Grits, 12 to 30 feet. Calcareous sands and grits seen at 



\ Nothe Fort, W^eymouth, near Osmington, etc. G. dilatata, etc. 



The term ' Kimeridge Grit ' was applied by Mr. R. Damon to a 

 very fossiliferous layer of pale gritty limestone about eight inches 

 in thickness which occurs a few feet above the Sandsfoot Grits, at 

 Osmington and Ringstead Bay.^ It contains Isastrcca Greenoiighi, 

 Thainnastrcca conciiDia and Thecosmilia, Ammonites viutahilis, Pcc/cn 

 vimincus, Lima pcdiniformis, PhasiancUa striata, etc. ; this is the 

 Upper Coral Rag, and on this horizon comes the Ironstone series 

 of Abbotsbury, attaining a thickness of about 35 feet. The iron- 

 ore is oolitic, and is well developed around Abbotsbury, where many 

 fossils are to be found in it, especially in the red lane to the north 

 of the village. They include Ammonites decipiens, Exogyra virgula, 

 Rhynchonella corallina, R. inconstans, Teixhratula subsella, Waldheimia 

 lampas, W. Dorsetensis, Echinohrissiis sctitatiis^ etc. The fossils of 

 this Ironstone as well as of the Kimeridge Grit have been described 

 as Kimeridge Passage-beds, but they are most properly included in 

 the Corallian series. 



Large slabs of the Trigonia-bed, containing 60 or 70 specimens, 

 have been sometimes obtained from Osmington, near Wej'mouth.^ 



Economic products, etc. 



The iron-ore (hydrous oxide of iron) of Abbotsbury, in Dorsetshire, is developed 

 around the village, on St. Catherine's Hill, etc., where the deep red colour of the 

 soil is very conspicuous. It yields about 43 per cent, of ferric oxide in mass, 

 although the oolitic granules contain about 73 per cent, of ferric oxide. The 

 matrix, however, contains a good deal of silica (42 per cent.), which lessens the 

 commercial value of the ore.'^ (See Fig. 49.) 



At Westbury in Wiltshire there is " an oolitic ironstone more or less 

 mixed up with black argillaceous ore. It is almost free from grit, and exists 

 partly as ferrous carbonate and partly as hydrated peroxide." The ore is of a 

 bluish-green colour, weathering reddish-brown. It appears to be of limited 

 extent, and varies from 11 to 14 feet in thickness ; it yields 37 to 42 per cent, of 



^ Damon, Geology of Weymouth, 1884, p. 65. 

 ^ J. F. Blake and W. H. Hudleston, Q.J. xxxiii. 272. 



^ J. Buckman, Trans. Dorset Nat. Hist. Club, ii. 19 ; Damon, Geol. Weymouth, 

 etc. , frontispiece. 



* Damon, Geology of Weymouth, 1SS4, p. 48. 



