Vol. 62.] TAEANNOX SEEIES OF TAKANNON. 687 



are in a more or less vertical position, and much disturbed. In 

 the bed and northern bank of the Fachdre below Plas Pennant, 

 papery but rather sandy shales, compact calcareous mudstones, 

 and small flags are twisted up, folded, and faulted. Some of the 

 darker shaly bands yielded a few poor fragments of Climacograptus 

 rectangularis and CI. scalaris, while just below the path from the 

 farmhouse down to the stream (3 in fig. 6, p. 686), Miss Elles was 

 fortunate enough to hit upon a fossiliferous band among some dark 

 sandy mudstones, which yields in relief : — 



Dimorphograptus Swanstoni, Lapw. I Diplograptiis vesiculosus, Nich. (v. R). 



(v. C). Monograptus tenuis, Portl. (f. C). 



Climacograptus medius, Tornq. (v. C). I Orthoceras sp. 



Climacograptus Hughesi ? (R). | 



This fauna is so distinct from any detected elsewhere in the 

 district, that it must not only constitute a special zone, but must also 

 be referred to a fresh group of strata, for which I suggest the name 

 of P a c h d r e. This Pachdre Group constitutes the lowest member of 

 the Llandovery Series found in the Tarannon district, and may be 

 distinguished as the zone of Dimorphograptus Sivanstoni* 

 It must have a thickness of 100 to 150 feet. Its junction with 

 the overlying Dolgadfan Beds is obscure in this section. 



Xo further palseoiitological evidence has been obtained from the 

 rocks in the upper part of the Pachdre Valley. The beds are at 

 first much disturbed, but gradually assume a north-westerly dip ; 

 and, judging from graptolitic evidence obtained in the Conroy 

 Valley, only a third of a mile to the north, there can be little doubt 

 that the various members of the Llandovery and Tarannon Series, 

 at any rate as high as the Brynmair Beds, will be found again to 

 the west. 



Thus, in this Afon-Fachdre section, the Upper Brynmair Beds 

 with their usual characters are seen to be faulted against a broken 

 anticline of Llandovery strata on the east, but to follow them 

 conformably on the western side. 



Although the Lower Brynmair Beds are faulted out in the Pachdre 

 section, yet they come in again much disturbed a quarter of a mile 

 higher up the Twymyn Valley, where they yield Bastrites Linncei, 

 Monograptus i-uncinatus, M. jaculum, and M . turriculatus ; and 

 some 200 yards to the west, Pachdre Beds are exposed at the 

 corner of the road from Pennant to Pentre Cil-cwm. Here Mono- 

 graptus tenuis and Climacograptus medius were obtained from 

 some sandy micaceous shales, weathering to a bright reddish-orange 

 tint, and associated with flags of 2 to 3 inches in thickness. 



No sections are seen in the valley of the Twymyn for the next 

 mile and a half of its course, but west of the river, along the 

 road to the north-east of Pennant-isaf, there is an exposure of 

 Llandovery rocks, possibly referable to the Monograptus-jimbriatus 

 zone. The graptolites, which are wretchedly preserved, include 

 the following : — 



Climacograptus scalaris (C). I Monograptus triangulatus 1 (f. C). 



Climacograptus rectangularis (f. C). Monograptus regularis (R). 

 Monograptus fimbriatus? (f. C). J Monograptus tenuis (R). 



