]>art 12 ( AI{|U»MFi:i{«M 9 i.imkskink uf s. wai.ks COAI.KIKLU. 1 I'i 



j»art. In st» far as ri)|K'r C aii<l S^ can Ue si'parately distin- 

 guislu'il, Gnuip 11, with Syriii;/othi/rl,s cf. cKxpidata and altundant 

 Cifufhophyllum tf,, ivpivsents V]}\m' C,; wliiK' Gronj) 12, with 

 abundant LifhoxtrotioH, repi-esonts S,. 



Westwards from the Ely valley, the se^uenee in the 

 standard limestones of C, and S,, so far as it ean ]>e determined, 

 appears t<» ])ersist t») the extremity of our distriet without sub- 

 stantial modilieation : hut, owini^ to the ahsenee of ex])osures, the 

 S limestones of (ii*(»u]) 12 liave not been tnieed nnieli more than 

 half-a-mile west of Miskin. 



Eastwards from the Ely valley, the crinoidal limestones of 

 Group 10 have not been reeoij^ni/.ed east of Croftau, but higher 

 beds, still jn-eserving the eharaeter of limestones with an abundant 

 >tandard fauna, are exposed a mile and a half farther east, in 

 Creigiau Quarry. In the distance of 2i mdes from Creigiau 

 < Quarry to the Taff. exj)osures are jHMtr, and throw little light on 

 tlie lateral change which converts almost the whole of C^ and S, 

 into a nearly-barren series of dolomites in the Taff 

 valley.' The characters of the series t)n the eastern side of the 

 Taff gor»,'e are descril)e<l on ]). LIO. 



It nMuains to specify the chief cx])osures of the standard 

 limestones of G, and S^ \\\ the outero}) west of the Taff. The 

 exjK)sures will l>e taken in order from west to east, and descriptions 

 conlined to a statement of horizon (cxce])t where special features of 

 lithology or fauna call for notice ). 



Old Quarry (Glain. H S\V X 2). on tho north side of tho road 3iMi yar-ls 

 sonth-west of Pont-y-Khy<l, on the western side of the Dawen valley : Hi>i)a- 

 rently the base of the yrey oolite 11. with the topmost beds of the underlyinir 

 (•rinoidal limestones 10. 



Cni^'s extending eastwards from the luunlet of City, north of Llansannor, 

 and t^Tuiinatin^' on tlie west in a (juarry behind the <-'ity Inn: the {rrey 

 «H»lite 11. highly crinoidal. 



tiuarry Kilani. 11 NK X 7), in Coed-y-Fforost. south of LlanhaiTy Staticm : 

 a ^roo<l exposure of the crinoidal limestones of (Jroup 10. seen to a thickness 

 of nearly 100 feet. Some shaly partinicrs and dohmiitie beds, and some 

 bn-eciation due to eontemporancons i-rosion. Cnninin rijlimlf'ira is eonimon. 

 Mirht'linid <jmmU« occurs. Hud i'lnnicfptt cf. Iiordrfintin is aV>undant. 



Old (.^"'irry at thf roa<lside 450 yards west of the last-named cjuarry : tho 

 prey oolite of proup 1 1. 



6l<l Quarry ((Jhun. V2 NW X 10). at the s(»uthern end of t'oed Gellihir-pinol. 

 between ]ir>nisad<ller and ]\Iiskin : th*- juncti«)n of crinoidal limestone an<l 

 iM.lite. at tlie top <.f 10 aii.l ba^r <»f 11. 



' A reci'iit I'xamiiiatKiii uf the old wnrkiiip's uf tli<' (.sirtli iroii-mijii- ha>* 

 • vealeil two bands of oolite within the «'ont4'mj»onineous dolomit«'s that 

 underlie tlie Sfiniitnhi Oolite in (iarth W««m1. Ii«.tli these o«ilit«-ban<ls have 

 suffered very ext^Misive subsiMpu'nt dolomitization. The lower ban<l may 

 represent either the i'lniinia Oolite or souje part of C .. The upp«'r band can 

 be assigned without d«»uV»t to C, -»-S, : it is probably identical with the band, 

 sliown in our diapnim of the TafTs Well and Tonpwynlais se«|uen«*e (vertical 

 sections, tip. 2. p. llJM.of which evi«len«'e is furnished in C. + S, on the eastern 

 side of the Taff p<»rpe by surviving patches «»f unaltered <M>lite (p. ITiO). 

 T. F. S..J»l>, Ith. lUIs. ' 



