140 



MR. F. DIXEY X^D PROF. T. F. SIBLY 02^' THE [vol. Ixxiii, 



Old Quarry (Glam. 42 NW X 21), beside the road 400 yards north -north-east 

 of the cross-roads at Miskin. 



Old Quarry (Glam. 42 NW X 20), at the Castell-y-Mynach Arms, west-north- 

 west of Croftau. 



Quarry (Glam. 42 NW A 18), 350 yards north of Croftau. 



Old Quarry, 300 yards north-east of Brofisein Quarry, near Groes-faen. 



In the last-named exposure, the Caninia Oolite has been traced 

 a little to the east of Groes-faen. Neither the Laminosa Dolomite 

 nor the Caninia Oolite has been recognized farther east. Both 

 become merged in the series of dolomites which constitutes the 

 whole of C, in the Taff valley.^ 



Upper Caninia Zone : 02 + 8,.^ 



The series, C, -|-S^, includes all the beds between the Caninia 

 Oolite below and the Main Seminula Zone (S.,) above. Its upper 

 limit, the base of S.,, is defined b}'' the appearance of Cyrtina 

 carhonaria. Essentialh^, this is a series of standard limestones in 

 which C^ and S^ are faunally continuous ; but a Mocliola phase is 

 found to form the base at the only locality Avhere that horizon is 

 exposed. 



Exj)osures east and Avest of the Ely River, in the neighbourhood 

 of Miskin, enable us to establish the following general succes 

 sion : — 



C-f-S^] in the neighbourhood of Miskin. 



Feet. 



( = Horizon ^). 



^1 2. Thinly -bedded limestones of very varied char-"] 

 acter, including crinoidal-shelly limestones, 

 oolites, and black calcite-mudstones. Litho- 

 strotion martini abundant. \ 



< 11. Thickly-bedded, grey, crinoidal oolite, in part [> 150 

 current-bedded and contemporaneously brec- 

 ciated. Occasional bands of dark, thinly- 

 bedded, gasteropod - limestone. Cyatlio - 



1^ phylhnn (p abundant. 



flO. Thinly-bedded, dark, crinoidal limestones.^^, 

 Beds of dolomitic limestone or finely-crys- 



I talline dolomite, and partings of shale or 



J shaly limestone occur, but are subordinate. 



] 9. Modiola pha-e : a varied group, comprising 

 calcite-mudstone, dolomite, oolite, breccia, 



I etc. Over 16 feet thick (dii-ect measure- 



[_ ment). 



0. Modiola phase.- — This is exposed in an old quarry behind 

 the Castell-y-Mynach Arms, between Croftau and Miskin, wliere 

 it forms the top of the quarry-face and is seen to rest upon an 

 uneven surface of the Caninia Oolite. The top of the phase is not 

 seen. The details of the section are as follows : — 



Lower C.,. 



200 



' But see footnote on p. 143. 



- Equivalent to the Upper Syringothyris Zone(C.^) and the Lower Semi)iida 

 Zone (S,). 



