170 MISS G. E. ELXES ON THE RELATION OE THE [May I9°9> 



refers to Conway Castle as standing 



' on the very top of the Bala Beds, somewhere about where the Hirnant 

 Limestone ought to be.' 



Unfortunately, lie afterwards accepted the view that the rock in 

 question was the equivalent of the Bala Limestone. 1 In the light 

 of recent work, his earlier opinion would seem to be more correct. 



Prof. Lapworth, 2 in his classical work on the ' Geological Distri- 

 bution of the Ehabdophora,' records the existence of graptolites in 

 the Taraunon Shales of the district ; he also gives reasons for 

 believing that the beds containing them correspond with the Lower 

 Gala Group of the South of Scotland. 



In the second edition of the Geological Survey Memoir of North 

 Wales (1881) pp. 280 et seqq., the succession of rocks at Conway 

 is tabulated. The Llandovery Beds are said to be absent, and the 

 Tarannon Shales are supposed to rest by unconformable overlap 

 upon beds not much higher than the Bala Limestone ; they are 

 also stated to form a narrow band at the base of the Denbighshire 

 Grits, from Conway to Llanbedr, a distance of 5 miles. The 

 Denbighshire Grits are estimated as 3000 feet thick ; and in the 

 Appendix, certain black shales are regarded as having a Llaudeilo 

 fauna, but their relation to the Bala Beds is therefore regarded 

 as being abnormal — they are said to be ' altogether bounded by 

 faults.' The main faults of the district, namely, those of Pen- 

 maenbach and the Conway estuary, are also referred to. 



In 1896 3 a short paper was published, in which the discovery in 

 the district of beds of Upper Bala (Ashgillian) and Upper Llando- 

 very age was recorded. 



(B) Petrological. 



In the Survey Memoir 4 there are a few references to the Conway 

 Mountain Lavas, including the so-called ' nodular felsites ' ; and a 

 brief description is given of the Penmaenbach rock, which is 

 termed a ' felspathic porphyry.' 



In 1882 Prof. Bonney, 5 in a general paper on ' Nodular Felsites 

 in the Bala Group of North Wales,' refers both to the nodular rocks 

 of the Conway District and to some of the other lavas. A brief 

 description of the Penmaenbaeh rock is also given. 



In 1885 Prank Butley, in the Geological Survey Memoir on the 

 ' Pelsitic Lavas of North Wales ' (p. 17), described one of the typical 

 lavas from Conway Mountain. 



1 ' Letters & Extracts. &c.' 1871, p. 440, footnote. 



2 Ann. & Mag. Nat. Hist. ser. 5, vols, v & vi (1880) pp. 45, &e. 



3 G. L. Elles & E. M. R. Wood, Quart. Journ. Geol. Soc. vol. Hi, p. 273. 



4 ' The Geology of North Wales' Mem. Geol. Surv. 2nd ed. (1881) p. 137. 



5 Quart. Journ. Geol. Soc. vol. xxxviii, p. 293. 



