﻿Vol. 66.'] TKEMADOC SLATES OE SOUTH-EAST CAKtfARVONSHIRE. 161 



but this requires much knowledge and skill. The higher flags, with 

 1 needle-rock ' between, contain Bellerophon and Asaphellus in some 

 abund&ace. 



(5) The Penmorfa Beds. 



Closely related to the beds quarried along the wharf at Portmadoc 

 are the coarse-textured banded needle-slates which overlie them- 

 These contain a distinctive fauna, and are so generally fossiliferous 

 that I have thought it well, although I cannot separate them with 

 great precision on the map, to give them a distinctive name. This 

 name I have chosen from the village in the street of which I find 

 the best exposure and the richest assemblage of trilobites. 



Unfortunately, about Penmorfa there is no open section where 

 the 100 feet of rock which separate the gritty beds from the fossil 

 band can be examined. Such rocks as can be seen in the fields 

 and roads west of Penmorfa are generally thin-bedded, shivery, and 

 presenting occasional coarse bands, which are notably micaceous. 

 They are everywhere pyritous ; in wet places they rust with an 

 inky aspect, and where reasonably dry become brightly ochreous. 

 South of the village the fossil band can be dug out of the cattle- 

 track which leads down to the Morfa. Below the fossil band the 

 section is obscure for about 15 feet, and the next exposure is of a 

 flaggy rock. This flaggy rock, which is seen to a thickness of about 

 30 feet, has alternating bands of harder and softer material. It 

 passes down into dark blue-black slates, which weather into long, 

 blade-like splinters and contain Asaphellus. 



The fossil band of Penmorfa occurs in the village-street at the- 

 fork of the New and Old Carnarvon roads between Capel Garisim 

 and the Post Office. Possils are also found in the raw rock shown 

 behind the cottages, south of the three roads and west of Bwlch- 

 edwin. The fossiliferous rock appears again in the corner of the 

 playground of the village school, and ranges continuously up the 

 hill almost to the new reservoir, from which the village now takes 

 its water-supply. Near the Capel (chapel) blue and brown mica- 

 ceous flaggy beds contain large trilobites, such as Dicellocephalus 

 and the broad form of Asaphellus. It is the beds above these, rather 

 fine smoothly-bedded but earthy slates, which yield the richest 

 fauna : Shumardia, Holometopus, Agnostas, Macrocystella, Sym- 

 physurus, along with the larger Asaphellus, Cheirurus, and Angelina 

 being characteristic. So far as I can discover, the fossil bed with 

 Shumardia is only 8 feet thick, but the bigger trilobites are found 

 through a much wider range of strata. Below the Shumardia Band 

 at Penmorfa Angelina is very rare, while above that band one can 

 be sure of finding fragments of Angelina in almost every bed. 



At Portmadoc the outcrop of the Penmorfa Beds is built over by 

 the houses of the suburb of Garth. There they are seen as rusty 

 grey-blue or leaden-grey needle-slates, with some coarser mica- 

 bearing bands, and have yielded many fragments of big trilobites. 

 At Pen-y-clogwyn and at the entrance to Morfa Lodge they are 

 better exposed, and in the old days provided Homfra and Ash 



