104 BRITISH FOSSIL CRUSTACEA. 



14. ROWLESTONE SECTION, AND CuSOP BEDS NEAR HaY. FLAGSTONES OVERLYING THE 



Lower Cornstones. 



The geologist who wishes to study the correlation of these strata should first visit the 

 town of Hay in Breconshire. 



In that interesting district the Old Red Sandstone is denuded into lofty hills, with the 

 Wye flowing on the line of denudation between them and the Radnorshire Silurians, 

 upcast on the north and north-east. 



Descending downwards from the upper crests of the " Brownstones" of the Black 

 Mountains, and where portions of Old Red conglomerate still linger, we pass from Brown- 

 stones into thin Cornstones (Upper Cornstones), in which, only last summer, in company 

 with Mr. Thomas, of Hay, I detected a portion of the dermal plate of a Scaphaspis. 

 These Cornstones overlie and pass downwards into greenish and grey sandstones, with 

 beds filled with layers of carbonaceous matter. Years ago speculations were entered into 

 for sinking for coal on the east side of the ravine above Cusop, two miles south of Hay, 

 and much money was sunk in these equivalents of the Rowlestone beds. 



Below these flaggy beds (Cusop carbonaceous beds) there are other Cornstones, as 

 seen in the section between Hay and Mouse Castle, and from these Cornstones came the 

 large Fish spine exhibited by myself at the late meeting of the British Association at 

 Edinburgh (1871), and named Onchus major by Mr. Etheridge, as being the largest 

 known spine from the Lower Old Red yet discovered. 1 To the north-west of the town of 

 Hay the lower beds of the Old Red with greyish sandstones and carbonaceous remains 

 pass into the Upper Silurians of Radnorshire. 



Now, he who examines the Rowlestone district near Pontrilas and Abergavenny, and 



observes how, as near Hay, Cornstones pass upwards and are overlain by flaggy beds with 



carbonaceous remains, these flaggy beds always occupying a particular horizon, will have 



little doubt in correlating the Rowlestone and Cusop flags as belonging to the same rock 



series, and in concluding that they belong to an upper Cornstone series and not to the 



lowest. In short, they form a line of demarcation between the Lower Cornstones and 



the Upper thin Cornstones and Brownstones which are so unfossiliferous throughout all the 



region of the Old Red of the West of England. On the summit and flanks of Rowlestone 



Hill, south of Ewyas Harold, Herefordshire, these grey flags have been quarried. They 



furnished a new species of Stylonurus {St. Symondsii), which is not unlike St. Poivriei 



of the Devonian of Forfarshire, besides other remains of Crustaceans found by Dr. 



McCullough of Abergavenny, such as Praarcturus gigas, Woodward, &c. I have seen 



Fish remains in strata overlying these Rowlestone Rocks among the Black Mountains, 



and on the Darren, but the above are the newest relics of Crustaceans in the Old Red 



proper of which the writer is aware. — W. S. S. 



1 While staying at Penzance I have seen, in the Geological Museum of the Institute, portions of Fish- 

 spines from the Cornish Polperro beds which are associated with numerous remains of Scaphaspis and 

 Pteraspis, like Onchus major in structure.— W. S. S. 



