Vol. 56.] 



SHALES OF THE WELSH BORDERLAND. 



399 



In the higher horizons of the zone Monograptus riccartonensis 

 makes its appearance, and in the beds overlying these it occurs 

 to the exclusion of almost ever}' other form, huge slabs of slate 

 crowded with this graptolite being very common. It is abundant 

 throughout the best slate-beds, and seems only to disappear when 

 these are succeeded by the Pen-y-glog Grit. The Grit occupies a 

 fairly wide area south-east of Penarth Quarry, and on the eastern 

 flanks of Moel Fern a another series of hard slates is exposed : these 

 are extensively quarried. The lower beds evidently belong to the 

 zone of Cyrtoqraptus Linnarssoni, since they contain that fossil in 

 fair abundance and also the forms enumerated in Table VII, col. E. 



The beds that overlie the foregoing are not very fossiliferous ; 

 they contain only a few specimens of M. dubius and M. Flemingii 

 var. (?). The highest Wenlock Shales seen are exposed in a 

 small trial- working farther east, and these yield, in addition to the 

 two forms just mentioned, a colonus-like form : therefore they are 

 probably quite near the top of the series. 



The slates which succeed these beds are extensively quarried 

 in the Deeside Slate Quarries, and are undoubtedly of Lower Ludlow 

 age, since they contain M. colonus, M. JVilssoni, and M. bohemicus. 



Table VII. 



DEE VALLEY GRAPTOLITES. 



*0 



ill 



Zone of 

 Monograptus 

 riccartonensts. ' 



Zone of 

 C. Linnarssoni. 



Zone of 

 C. rigidus. 



=4-1 £ 

 O 



G 



Names of Species 

 and Varieties. 



[C ^L very common ; c = common ; 

 r = somewhat rare ; R = very rare.] 



Note. — There is no palaeontological 

 evidence of the C.-symmetricus zone 

 in the Dee Valley. 



A 



-i 



« 



c 

 c 

 c 



c 



c 

 R 



B 



a 



P 



S 

 a 

 U 



C 



c 

 c 



R 



C 1 



■e 



a 

 Ph 



c 

 c 

 c 

 c 



R 



C 2 



§ 

 c 



C 



D 



S 

 c 



C 



c 



E 



F 



c3 

 C 

 u 







eg 



S 







c5 



S 



"3 

 



Monograptus priodon (Broun) .... 



r 



c 

 c 



C 



C 



c 



c 



C 

 c 



c 



c 



c 



Retiolites G-einltzianus, Barr. 



Cyrtograptus Murchisoni, Carr 



Monograptus vomerinus (Nich.) var. a. 

 M. basilicus, Lapw , . . . 



M. riccartonensis, Lapw. .. 



M. duhius (Suess) 



Cyrtograptus Linnarssoni, Lapw. . . . 



Monograptus flexilis, sp . nov 



M. Flemingii (Salt.) var. a 



y 



" » 



2e2 



