Vol. 56.] FORMATION AND ITS GRAPTOLITE-FATJNA. 445 



Pigot, and at the Workhouse Dingle near Little Worthen. In the 

 beds of the Workhouse Dingle Moywgraptus vulgaris is abundant 

 and is associated with Reiiolites nassa, Holm, which has not hitherto 

 been recognized elsewhere in Britain. A good section through the 

 Upper Wenlock and Lower Ludlow is exposed along the Brockton 

 Brook, but graptolites are scarce and badly preserved. I have not 

 worked out the section in complete detail, and it may therefore be 

 passed over. 



(b) Ackley-Llettygynfaeh Section. — A fairly good section 

 through the Upper Wenlock and Lower Ludlow is exposed along 

 the lane from Lleyn on the south, past Ackley to Llettygynf ach, but 

 here again the graptolites are for the most part indifferently pre- 

 served and a zonal division of the rocks is at present impossible. The 

 beds for some distance above the Wenlock are not exposed : the 

 lowest visible horizons of the Ludlow contain M. chimcera or its 

 variety Salweyi, M. tumescens and its variety minor, and M. dubius ? 

 The exposure at Llettygynfach Farm is one of the type-localities 

 for M. tumescens : it is here the most abundant form, and so far 

 as is known at present occurs only here and at Ludlow. The 

 highest beds in this section have yielded one specimen of M. leint- 

 ivardinensis. 



(4) Montgomery-Road Section. 



South and west of the Long Mountain itself, but forming practi- 

 cally its longitudinal extension, lies a large area coloured on the 

 Geological Survey maps as Wenlock. I have not worked the country 

 in detail, but a section seen along the road from Montgomery 

 Railway-station to Montgomery Town is worthy of notice. 



The beds are much disturbed and are repeated by folds, so that it 

 is difficult to be sure of the order of succession, but two zones are 

 rich in graptolites. The lowest is that of M. Mlssoni, with which 

 are associated M. dubius, M. varians, and fragments of Retiolites sip. 

 The higher zone is that of M. leintwardinensis var. incipiens. The 

 intervening beds are so crushed that it is impossible to obtain any 

 identifiable graptolites from them. 



The Ackley-Llettygynfach and Montgomery-road sections were first 

 worked out by Prof. Lapworth, who pointed them out to me when I 

 began to study the graptolite-fauna of the Lower Ludlow Beds, and 

 kindly placed his collections from those localities at my disposal. 



(D) Supplementary Districts. 



In addition to working over the three areas just described, I 

 have had an opportunity of examining graptolites from the Lower 

 Ludlow Beds of several other districts in Great Britain. Before 

 concluding my remarks on the stratigraphy of the Lower Ludlow 

 formation I will briefly point out to what extent the graptolitic 

 evidence obtained from these supplementary districts confirms the 

 conclusions already arrived at in the Ludlow, Built h, and Long 

 Mountain districts. 



Q. J. G. S. No. 222. 2 h 



