Vol. 5 i.] 



SERIES OF SOUTH DENBIGHSHIRE. 



19 



intervals, together with fragments of crinoids. It is as a rule 

 most easily found in the gritty bands, especially on their under 

 surfaces. Farther north, opposite Pandy, I obtained M. Nilssoni, 

 and near the head of the incline at the village Beyriclria Kloedeni, 

 Chonetes minima, encrinite-stems, and an indeterminable graptolite. 



The top of this hill is formed in part of a different material. The 

 slates are there pale, and a pale-coloured grit occurs : it is pro- 

 bable that these belong to the gritty series above the flags rather 

 than to the Nantglyn Flags themselves. 



Farther east the Nantglyn Flags form the lower part of the 

 western and northern faces of the hill east of Nant-y-gro, and 

 M. colonus occurs here also. 



The following is the list of fossils found in the Nantglyn Flags in 

 this area : — 



Orthooeras primcevum, Forbes. 



„ SedgwicJci, Forbes. 



„ ventricosum, Sharpe. 



Cardiola. 



Chonetes minima, Sow. 

 Beyrichia Kloedeni, M'Ooy. 

 ' Actinocrinus ' pulcher, M'Coy. 

 Monograptus colonus, Barr. 



Upper Gritty Beds. 



Concerning these there is but little to say, as no fossils have yet 

 been found in them. On the hill east of Nant-y-gro the M. colonus- 

 beds are succeeded by a series of alternations of slaty and siliceous 

 beds, which form the upper part of the hill, but are there mostly 

 concealed by the heather. They dip at a low angle towards the 

 east under the somewhat less gritty beds of the next division ; and 

 reappear with a more southerly dip in the road-metal quarry at 

 the side of the Holyhead road in Wriddiog. Here they are very 

 compact and dark blue in colour, banded with numerous regular 

 pale-coloured siliceous bands an inch or two in thickness. There is 

 a peculiar thin bed here which breaks up with the greatest ease 

 into thousands of small cubical or rectangular blocks. 



It should be noticed that the hard siliceous bands in this series 

 are generally compact and fine-grained; so that in strictness 

 perhaps the term ' grit ' ought not to be applied to them. 



Leintwardinensis-Beds. 



These are found near Pen-y-vivod at the southern end of Wriddiog. 

 In general appearance they are not unlike the Nantglyn Flags and 

 are streaked with narrow bands of fine grit ; but the surfaces of 

 these bands present a characteristic glistening appearance due to 

 small scales of mica, and this generally serves to distinguish them 

 from any of the beds below. Another peculiarity which these beds 

 have is that they break up into very long, narrow, prismatic blocks. 



At the side of the path from Pen-y-vivod, a little north of the 

 dyke already mentioned, there is an exposure of these rocks in 

 which Monograptus leintwardinensis, Lapw., occurs abundantly ; 

 and Orthoceras and Chonetes minima have also been found. 



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