﻿158 ME. W. G. FEAENSIDES ON THE [May IC)IO,. 



piece of which when broken open is fit for preservation in a museum. 

 North of Wern the exposures are more difficult, and I shall only- 

 mention the old tramway -cutting at the 200-foot contour east of 

 the bridge over the Tyn-llan road ; the field opposite Wern Lodge ; 

 and the quarry for road-metal at the 300-foot contour close to the 

 second milestone out of Tremadoc, on the southern branch of the 

 Carnarvon road. 



Exposures on the Criccieth side of the anticline are difficult to 

 work, for their cleavage is overwhelming, the dip steep, and the bed 

 determines only a hollow in the moorland. Loose slabs with soma 

 Dictyonema are nevertheless not infrequent among the heather. 



Along with the Dictyonema occur usually a few elongate Lingula, 

 cap-like Acrotreta, and especially spicules of a sponge which may be 

 Protospongia. I have also found occasional tails of PsilocepJialus^ 

 loose thoracic segments of some broad and large trilobites, and the 

 head of some Peltura-like Olenid and of another trilobite not unlike 

 Hysterolenus tomquisti. The Protospongia is especially characteristic 

 of the harder slates which overlie the Dictyonema Band. 



(3) The Moelygest Beds. 



Above the Dictyonema Band come a series of rusty- grey slaty 

 mudstones which appear to be almost devoid of fossils. For this 

 subdivision of the Tremadoc Series, from the circumstance that it 

 forms the underscarp and dip-slope of Moel-y-gest, I have taken the 

 name Moelygest Beds. 



The best continuous exposure is along the road-cutting behind the 

 wharves at Portmadoc, south of, and beneath, the rock which has 

 been so extensively quarried. The bulk of the rock is an ill- cleaved 

 dark- grey mudstone, sometimes splintery, but usually more noticeable 

 by the obliqueness and rippled surfaces of its joints. 



The following subdivisions may be distinguished : — 



Thickness in feet. 



Dark -weathering bladed rusty slate, fine-grained and dark within, 

 ioints verv much rippled -where they cross coarser and finer 

 beds 100 



Paler-weathering blue slate, with very occasional white- 

 weathering pyritous spots. Some gritty partings, also a well- 

 marked band of cone-in-cone ironstone nodules, which some- 

 times run together as a continuous bed = .. 50 



Strongly banded, tough, rusty -weathering, dark-grey slate with 

 rippled j oin ts 40 



Very uniform, blue-grey slate, with some white-weathering 

 pyritous spots forming a passage-zone to the Dictyonema 

 Band and like it containing Frctospovgia 50 



Total 240 



Along the dismantled tram-road above Penmorfa the banded 

 beds are beautifully seen in the cutting east of the Carnarvon-road 



