OF RHYMNEY AND PEN-Y-LAN, CARDIFF. 479 
intersecting sets of folds, however, is clearly evident, and makes 
itself inconveniently felt in the great irregularity of dip and strike 
to which it sometimes locally gives rise. 
Succession of the Silurian Strata. 
Unless the anticlinal axis of Pen-y-lan hill rises as it passes east- 
wards towards Rhymney, the beds exposed in the ditch below Pen- 
y-lan House, on the axis of this anticlinal, must be the oldest in 
the neighbourhood, and give us therefore a convenient base-line to 
work up from, the more so as the quarry in Pen-y-lan hill lies on the 
line of strike of the axis and not far from its exposure in the ditch. 
Pen-y-lan Quarry.—tThis will be found in a field on the side of 
Pen-y-lan hill, a little south of the “y” in “ Pen-y-lan” on the 
Ordnance Map. It exposes yellowish and greenish-grey mudstones 
and fine argillaceous sandstones, rather thickly bedded, and tra- 
versed by two sets of joints, which, together with the bedding- 
planes, divide the rock up into a number of roughly cubical blocks. 
These weather into a spheroidal form, and exhibit an incipient con- 
cretionary structure, both concentric and radiating. 
The beds strike nearly W.N.W., and dip at an angle of 30° to the 
N.N.E. 
Feeling dissatisfied with my own determination of the fossils I had 
collected here and elsewhere in the district, I submitted them all to 
Mr. Etheridge, who with great kindness prepared the lists which are 
given here and subsequently in the paper. I have ventured to incor- 
porate with the fossils from Pen-y-lan those named for Mr. Norman 
Glass by Mr. Salter. 
Fossils from Pen-y-lan. 
(The range of the species is not carried below the Silurian in cases where they 
descend into the Upper Cambrian.) 
Llandovery.| Wenlock. | Ludlow. 
Petraia bina, LOonsd............0..00.e00e0- * * 
Cyathophyllum elongatum, Phil. ...... * 
Lingula cornea, Sow. ............06 SP ees. sed cope a ciponNL e R * 
Atrypa reticularis, Lin. ..........ceceeeee * * * 
Leptzena sericea, Sow. .............000e0ee % 
transversalis, Dalim. .........0000.. % % 
Strophomena euglypha, Dalm. ......... x * * 
compressa, SOW. ...........0-- seen. * * 
Spirifer plicatellus, Linn. ............52. % # * 
Meristella tumida, Dalm. ..............- % * * 
Avicula planulata, Conr...... boatoecn Siete % * * 
Ambonychia tumida, Soll. 
Murchisonia pulchra, M‘Coy ............ * 
Bellerophon dilatatus, Sow, ............ % * 
Phacops caudatus, Brin. ........c0000 * * * 
longicaudatus, Murch. .........60 * * * 
Stokesii, Hdw. ....... eeeoieenaeese ae % * % 
IAGIGARPISICOLONALAR ISTIC) vesceenecssses||) ceeees | ||  cceneee % 
Tileenus barriensis, Murch. ..........0000-| saeees % * 
Calymene Blumenbachii, Brongn. ...... @ * 
Cheirurus bimucronatus, Murch. ...... * * 
Encrinurus punctatus, Briimn............. * * * 
WAMLOLAMIS EB NONG Da vetcreiscsesiecnce|| © Uses * 
ORIG sw Nor 1ls9: Db Ti 
