482 Prof. Sedgwick on the May Hill Sandstone, 



The above great and ill-defined group seems to range through 

 the water-shed last mentioned, and so to pass under the Wen- 

 lock escarpment. On the southern side of the valley between 

 Llandovery and Llangadoc the same group is exposed, and from 

 various quarries (e, g. Pen-y-lan, Goleugod, Cefn llhyddan) I 

 obtained the species described by Professor M'Coy in his List of 

 the Cambridge Palaeozoic Fossils. As among them were some 

 species which rather seemed to indicate a May Hill group, it 

 became important to re-examine some of the localities, which I 

 will notice in the order in which we visited them. 



1st. Fenian (or Pen-y-lan), a little more than a mile E.S.E. 

 of Llandoveiy. 



The quarry with the fossils is near the crest of the hill, and 

 contains some beds of sandstone, alternating with a decomposing 

 flagstone and indurated shale. It' was formerly used for building, 

 but is now deserted. The beds dip at a great angle about N.W. 

 Some of the beds of the ridge, which ranges to the N.E., are 

 nearly perpendicular. In a new quarry, nearly a mile towards 

 the N.E., and at a lower level, we found the beds dipping about 

 S.E. at an angle of 70°. We believe it .almost impossible to 

 determine, by the evidence of sections, what exact relation the 

 Penlan beds bear to the rocks in the immediate neighbourhood ; 

 but among the ruins of the deserted quarry we collected the 

 following species : — 



Halysites catenulatus. Stenopora fibrosa, 



Petraia uniserialis. Pentamerus globosus, 



bina. oblongus (very abun- 



Palaopora megastoma. dant). 



This list does not contain any species which has hitherto been 

 regarded as exclusively characteristic of Cambrian rocks, and it 

 gives us a true and characteristic May Hill group of fossils. 



2nd. Two quarries from the Goleugod ridge, near the road on 

 its north side, and a third quarry on the cross road to Myddfai 

 gave the following results : — 



Ist quarry — 



Halysites catenulatus, , Spirifer percrassus (very abun- 



Favosites alveolaris, dant). 



multipora. Pentamerus undatus. 



Ceraurus Williamsi, Or this calligramma. 



Lituites comu-arietis. 



The corals and the Pentamerus are well-known common types, 

 the others are exclusively Cambrian ; therefore the group is 

 Cambrian, as it does not give one exclusively Silurian type. 



