154 



WALTER KEEPING ON THE 



At Cwni Symlog, nine miles east of Aberystwyth, pale soft shales 

 and slates with thin grits, rich in fossils, are found. 



Kastrites peregrinus, Barr. 

 Monograptus Sedgewickii, PortL 



crenularis, Lapw. 



cypkus, Lapw. 



gregarius, Lapw. 



intermedins, Carr. 



Olingani, Carr. 



spiralis, Gein. 



lobiferus, M'Coy. 



runcinatus, Lapw. 



■ Hisingeri, Carr. 



tenuis, Portl. ? 



involutus, Lapw. 



Diplograpsus tamariscus, Nidi. ? 



- Hugnesii, Nick. 



sinuatus, Nidi. 



Fossils from Cwm Symlog. 



Monograptus palmeus, Barr. 

 Cliinacograpsus spiralis, His. 



FORAMINIFERA. 



Dentalina. 

 Textularia. 

 Eotalia. 



Annelida. 

 Nereites Sedgwickii, Murch. 

 Myrianites M'Leayi, Murch. 

 Nemertites Olivantii, Murch. 



Algm. 



Buthotrephis major, Keep, 



minor, Keep. 



minimus, Keep. 



At Ystrad Meurig, forming the high ground twelve miles south- 

 east of Aberystwyth, and in near association with a fossil zone, is a 

 series of hard pale grits with thin indurated slate partings, firmly 

 bound together, to form hard massive rocks (a) ; we refer to this as 

 the " Strata Florida rock." 



Another well-marked rock demanding attention is (b) a pale indu- 

 rated slate rock, usually cross-banded by thin arenaceous stripe- 

 zones. It is well seen at Machynlleth, to the east of Eglwys Fach, 

 and east of Tal y bont. Again, the same type of rock occurs (c) in 

 the hills east of the Eheidol gorge ; I find blocks of it around Llan- 

 trisant; and it is also well developed at Goginan, to the east of 

 Llanddewi Brefi, and in the hills west of Ehyader. These rocks 

 are essentially similar to those of Ystrad Meurig, only less arena- 

 ceous ; and I include them all under the name of "Strata Florida 

 rock." 



Now, classifying these various localities of the Strata Florida rock, 

 we find they fall into a set of definite lines having similar relations 

 to neighbouring rock-beds, and indicating, as I believe, definite 

 zones. First, the more arenaceous rock of Ystrad Meurig is in the 

 same north-and-south line with Cwm Symlog and with Llantrisant ; 

 and in the first two of these places it is in near relation with a rich 

 fossil zone. Also it is about in the same line with the Large-flag 

 series, as seen in the Devil's -Bridge road, nine miles east of Aberyst- 

 wyth, also found at Llantrisant and Cwm Symlog. In these places 

 we have, then, evidence of the occurrence of this hard pale slate rock 

 along a definite line of country in near association with the Grap- 

 tolite fossil-zone and the Large-flag series. Next we find that the 

 group b also falls into a line east of Aberystwyth ; and here, again, 

 it is associated with the great fossil zone at Machynlleth, while near 

 Tal y bont it is connected with a band of rottenstone like that of 

 the Large-flag series at the Devil's Bridge. 



Altogether, then, the result of these lithological correlations is to 

 support our theory of four different lines of north-and-south foldings 



