158 OBSERVATIONS ON THE 
This, which I have called the syntelism of the rocks, viz., the 
agreement of the sequence in one district with that in another, 
is strong evidence, and the fossil evidence, as far as it goes, 
confirms these identifications 
Gc. In the base of the Corwen Grit, near Corwen, I found— 
Orihis sp. Favosites alveolaris 
Petraia sp. 
From the same horizon (Gc.) near Penycae on the 8. side of 
Oyrnybrain :— 
Petraia subduplicata | Meristella crassa 
P. crenulata 
From Plasuchaf :— 
Petraia subduplicata Orthis protensa 
P. crenulata Meristella crassa 
From Ponthafodcynfor and S.E. of Llansaintffraid :— 
Favosites alveolaris Orthis elegantula 
F. fibrosa | O. hirnantensis 
Heliolites interstinctus O. lata 
Monticulipora lens Strophomena rhomboidalis 
Petraia crenulata Cyclonema ? 
Glyptocrinus sp. | Flolopella obsoleta 
Calymene blumenbachii Murchisonia carinata 
Tentaculites anglicus Macrocheilus fusiformis 
Berenicea heterogyra MW, angulata 
Glauconome disticha Platyschisma or Rhaphistoma 
Ptetodictyacostellata or fucoides Bellerophon 
Leptena transversalis Conularia sowerbyt 
Orthis calligramma Orthoceras 
The basement bed (G.) in this district is sometimes merely a 
sandstone, sometimes it is a grit, or even a conglomerate, and 
sometimes it is a limestone, while often it looks like a bed from 
which calcareous matter has been removed, leaving only the 
finer insoluble residuum now in the form of a white pasty 
mudstone. The occasional presence of such corals as /. a/veolaris 
would be enough to suggest that it might sometimes contain a 
sufficient number of calcareous organisms to form a band of 
limestone. I have elsewhere given a description of some 
sections in which it is well seen*. 
I will now add a note on the Hirnant Section. It seems 
to me that there have been two entirely distinct beds con- 
founded under the name Hirnant Limestone. There is a 
pale grey imperfectly cleaved fine textured clay rock, with 
numerous nodules of limestone, and containing Bala fossils 
such as Orthts actoniw, O. sagittifera, and LEchinospherites 
balthicus, and that on this rests a crystalline, often pisolitic 
impure limestone, the zone of Orthis_hirnantensis, which readily 
weathers into the dark gingerbread coloured rock in which 
fossils are fairly abundant, and from the weathered parts of 
which the casts can be easily procured; and that exactly the 
same varieties are observed at the same horizon in the Lake 
District (see p. 149) and, though less distinctly, in South Wales. 
*Q.J.G.S., Vol. xxxiii., p. 207. kKkuddy, Q.J.G.S., Vol. xxxv., p. 200. 
