pari 2 J ( ARnoMFKRous mmkstonk of s. walks COALFIKI.U. 139 



La in'nionu Dolomite. — Dark-ji^rev or hhu'-^n-.y tinely-ervstal- 

 liiK' (loloimtos, slii^'litly crinoidal towards tlie base, Imt otlierwise 

 apiKireiitly unfossilitVrous. In the lowest beds, however, rounded 

 I«tches of eoai*sely-ervstalline ealeite j>ossibly represent tlie re- 

 ervstallized intillinii^s of eavities in fossils.^ 



Tlie face of an old qiuirrv (Glani. 42 NW A 17) situate<l !oO 

 yards north of Croftau shows the l)ase of the Lamiiiosn Dolomite 

 in eontact with the nnderlyinii^ erinoidal limestones ; and a cutting 

 which runs northwards fr(>m the quarry exposes fidly 100 feet of 

 dolomite. 



The followiui^ are the chief exposures of the Laniinnsa 

 Dolomite, enumerated in oi\ler from west to east: — 



Old <^tmrry (Glam. 41 SW X 4), be.sitlo the road at Tyn-y-^auig. on the 

 western side of the Dawen valley, north of Craig Penlline. 



Old (c^iiarry. 150 yards south of St. Ann's Chapel, south of Brynsaddler. 



Old Quarry (Glam. 42 NW X 17), 150 yards north of Croftau ; and cutting 

 extending northwards from the quarry. 



Exposure on the northern side of Brofiscin Quarry, north of Groes-faen. 



Ca n in ia O o 1 i t e. — Essentially, i)ale-grey thickly-bedded oolite, 

 <»ften with imperfect stratification. The o(ditie structure is 

 variably eoarse or tine. The rock is typieally foraminiferal. 

 Current-bedding is frequent, and many current- bedded jXJi-tions 

 give evidence of contemj>oraneous erosion in an abundance of 

 angular or rounded fragments of oolite. Apart from crinoids 

 and foraminifera, fossils are almost confined to an abundance of 

 the brachiojx)d SchrllicicurUa cf. crenisfrio, or the gasterojxKis 

 lipllerophon and EuomplKthts, in rare bands. Si/riiufopnra cf. 

 (liKtans^ S. cf. reticulata, Sr/zt/iuila ci.Jicoiifes, and papilionaceous 

 Choiif'tps, occur rarely. In the main mass of the Caninia Oolite 

 crinoidiil bands are few, but near the top the rock may become 

 highly crinoidal, as seen in a (juarry north of Croftau (Glam. 

 42N\VaIS). The crinoidal l>eds at'this locality contain papili<.- 

 naceous C/ionrtrs, and have yielded a single corallite of Litho- 

 X trot I ON martini (/). 



In an old <juarrv at the Castell-y-Mynach Arms (Glam. 12 N\V 

 A 20), near Ci-oftiiu, the Modiohf pha.se of C^ is .seen resting u|)on 

 an eroded surface of the Caninia Oolite (see p. 141). 



The following are the chief exposures of the Caninia Oolite, 

 named in onler from west to east : - 



Old Quarry (Glam. 41 SW X 5), at the south-eastern end of Coed Mansel, 

 on the western side of the Dawen valley, north of Craig Penlline. 



Exposures in woods (Graig), 750 yards north-north-east of Llansannor 

 Church. 



Old Quarry (Glam. 41 NE \ H). a quarter of a mile south of Brjiisaddler. 



Quarry (Glam. 42 NW X 8), 200 yards west of Caer-gwanaf-uohaf, on the 

 western side of the Ely vallc}' near Miskin. 



' C{»mpare K. K. L. I>ixon. (Jower paper, p. 4H: 

 Q. .I.G.S. No. 2JK). 



