Vol. 62.] LIMESTONE OF THE MEXDIP AREA. 365 



160 yards above the quarry, is an old limekiln ; here, in a small 

 disused quarry and adjoining exposures, compact limestones, dipping 

 northward, show abundant Seminula ficoides and Productus sp. 

 Some 50 yards farther up the path, similar beds, with the same 

 fossils, are again seen dipping northward. Limestones of this litho- 

 logical character, and containing abundant Seminula ficoides, can 

 be assigned to S 2 with certainty. North-west of these exposures, 

 in two adjoining fields, is a considerable exposure showing hard 

 black limestones, dipping north-eastward at 55°. Finally, still 

 farther north-westward, are exposures on the site of two adjacent 

 disused quarries. Here, as in the uppermost part of Ebbor Rocks, 

 the beds dip south-westward ; the dip is 45° and the strike west 

 33° north. The upper beds are compact black limestones, with 

 abundant Seminula ficoides ; the lower beds are dark reddish 

 limestones, containing Liihostrotion Martini (very abundant), 

 Productus B (abundant), and Aihyris cf. expansa. The horizon of 

 this exposure is, therefore, Upper S x and Lower S 2 . 



(iii) The Carboniferous Limestone south and west 

 of the Valley. 



The north-eastern boundary of this mass of limestone marks the 

 course of a great thrust-fault, with an upthrow of about 2000 feet, 

 which has thrown Zaph?'entis-beds and Syringothyris-heds obliquely 

 against the shales of the Millstone-Grit Series, and reduced the 

 outcrop of that series to a narrow strip, about 200 yards wide, 

 running north-west and south-east. 



The Upper Zaphrentis-be&s are well exposed, near the north- 

 western extremity of the mass, in the bluff which rises on the 

 eastern side of the footpath leading from Lynchcombe Lane 

 (Westbury) onto the hills toward Priddy. The beds here exposed 

 are black crinoidal limestones, and contain a typical Z 2 fauna, 

 comprising Zaphrentis aff. cornucopia?, (abundant), Z. aff. Phillipsi, 

 Caninia cylindrica, Michelinia cf. favosa, Spirifer aff. clathratus 

 (common), Khipidomella aff. Michelini, Ortliothetes aff. crenistria, and 

 Chonetes cf. liardrensis ; they dip north-westward at about 50°, 

 their strike being N. 37° W„ The prevalent dip of the beds 

 throughout the mass is, however, southward. Z 2 is again exposed 

 on either side of the Priddy-to-Easton lane, about 200 yards east of 

 the bluff; here the dip is about 35°, southward. 



There are several exposures near the south-eastern extremity of 

 the mass, notably the limestone-scarp, facing north-eastward, on the 

 southern edge of Hope Wood. Yery near the south-eastern end, on 

 the track leading down to Ebbor Farm, just above the lane, are 

 some small limestone-exposures. The beds here contain Zaphrentis 

 aff. cornucopias, mut. C, Syringopora cf. distans, Productus aff. 

 Cora (?), Spirifer cf. bisulcatus, and Khipidomella aff. Michelini. 

 These beds, which dip southward, clearly belong to the Syringo- 

 thyris-Zone, and are, doubtless, in sequence with the Upper 

 Zaphrentis-heds. 



Q. J. G. S. No. 246. 2 c 



