70 DE. T. P. SIBLY ON THE FATJLTED INLIER OE [Feb. I912, 



A precipitous rock-face, about 85 yards east of the tuunel ( j:> on 

 the map, PL II, and in the text-fig. p. 6S), shows sharply-folded 

 limestones in its highest part and distorted beds of limestone, 

 with Productiis aff. giganteus in great profusion, below. Here the 

 whole quarry-face is formed of limestone. A little farther east 

 (r and s), however, only the lower part of the quarry-face consists 

 of limestone, the upper portion being formed of quartzites. Ap- 

 parently the limestones here dip steeply southwards, while the 

 superincumbent quartzites dip northwards, into the cliff. This 

 is the last exposure of beds belonging to the Grit-&- Shale Mass. 

 The recess at the eastern extremity of the quarry shows beds of 

 limestone much broken and veined with calcite. 



Other Exposures. 



(i) Sections in the railway-cutting. — A lamelli- 

 branch-fauna in the Upper Seminula Beds. — "With one 

 exception, the remaining exposures of Carboniferous Limestone, all 

 of which lie to the east of Yobster Old Quarry, present no features 

 of special importance. The exception is afforded by a small section 

 of the highest Seminula Beds, which lies in the northern bank of 

 the railway-cutting, about 60 yards west of the bridge on which 

 the road crosses the railway (t on the map, PL II). 



This section is one of many small exposures that are to be found 

 in the railway-cutting east of Yobster Old Quarry : exposures 

 showing disturbed beds of Carboniferous Limestone with no 

 constant direction of dip. Its importance lies in the discovery in 

 it of a band of limestone yielding numerous lamellibranchs. These 

 fossils occur in a thin band of light-grey compact limestone, in 

 association with abundant casts of an expansiform Athyrid. 



The lamellibranchs collected were submitted to Dr. AYheelton 

 Hind, who has kindly reported on them. 



Dr. Hind remarks that ' The sjDeciiiiens are very difilcult to determine. 

 Frequently the umbo and hinge-line are not exposed.' He determines 

 the following : — 



Schizodus sp., ' not nnlike [ TelUnomorpha (]) sp. 



Sch. truncaUiS King.' Gram^natodon (f) sp. 



Cyimcardella sp. | Cf. Tleuro'pliorus cosiatus Brown. 



So far as I am aware, this is the only record of a lamellibranch- 

 fauna in the Seminula Zone of the South- Western Province. The 

 horizon of the band is fixed as follows : — (1) a bed lying about 

 3 feet higher in the section yields LithostrGtion martini^ Carcino- 

 pJiyllum 0, and Productus aflt'. giganteus ; and (2) not more than 

 6 yards away from this section, in the opposite bank of the 

 cutting (n on the map, PL II), is a buttress composed of grey 

 compact limestones, in part brecciated and ' concretionary,' and 

 yielding Seminida Jicoides. This evidence fixes the horizon at the 

 top of the Seminida Zone. 



(ii) Old quarries. — In the disused quarry which lies in the 



