Vol. 51.] SERIES OF SOUTH DENBIGHSHIRE. 17 



Monograptus vomerinus, Nich. 



,, personatus, Tullb. 



„ priodon, Bronn. 



„ „ var. riccartonensis, Lapw. 



„ „ var. Flemingi, Salt. 



Eetiolites Geinitzianus, Barr. 

 Cyrtograptus Murchisoni, Carr. 

 Acroculia haliotis, Sow. 

 Orthoceras Sedgwicki, Forbes. 

 Orthoceras, sp. 

 Berwynia Carruthersi, Hicks. 



— together with fragments of encrinites and brachiopods. 



These slates are but little exposed in our area. There is a small 

 quarry in them a little south of the road from Glyndyfrdwy to 

 Glyn Ceiriog, about 1 mile north-west of Tomen-y-meirw. They 

 form, however, a widely-spread zone, and it will be sufficient to 

 refer to Caer Drewyn and Glyn Ceiriog as localities where they may 

 be studied in the Llangollen basin. 



Pen-y-glog Grit. 



This is well seen in the Penarth quarry, of which it forms the 

 top. It is generally a coarse felspathic grit, with narrow partings 

 of soft and shaly beds. ' Its thickness is not great, but, owing to 

 the fact that the dip nearly coincides with the slope of the ground 

 south of the quarry, it covers a wide area on the ridge of Moel-y- 

 Grwynt. It can be traced continuously to the summit of Moel Ferna, 

 and thence eastward for a distance of about 1 mile. Farther east 

 it is lost in the heather, and no satisfactory exposures are to be 

 found until we approach Llansaintffraid Glyn Ceiriog. It appears 

 to become thinner, or at least not so strongly marked, in this direc- 

 tion, and no longer forms the prominent feature which it does on 

 Moel Ferna and Moel-y-Gwynt. 



Fossils are not uncommon. At Pen-y-glog Dr. Hicks obtained 

 remains of plants which have been referred to Nematophycus 

 (N. Hicksii, R. Eth.) and Pachytheca, and also spores of what 

 appears to be a lycopodiaceous plant. On the ridge of Moel-y- 

 Gwynt and on Moel Ferna fragments of graptolites and brachiopods 

 occur. 



In the "Woodwardian Museum the following fossils are recorded 

 from the grit of Caer Drewyn, near Corwen, which is the northerly 

 continuation of the Pen-y-glog Grit : — Meristella tumida, Stropho- 

 mena depressa \_Leptcena (Strophomena) rhomboidalis], Phacops, 

 encrinite- stems, Petraia \Lindstroemia\ duplicata, var. tmiserialis, 

 and Favosites fibrosa (?). 



vol. xxxviii. 1882, p. 97); on specimens collected by myself; and on speci- 

 mens in the Woodwardian Museum. It may be remarked that Orthoceras 

 Sedgwicki, Forbes, is sometimes (but, I think, incorrectly) looked upon as- 

 a synonym of 0. subundidatum, Portl. 



Q. J. G. S. No. 201. c 



