Vol. 67.] THE CAEBONIFEROUS SUCCESSION IN GOWEK. 487 



abundant specimens of Belleroplion ; this, though sharply- 

 separable, on account of its far more intense dolomitization, 

 from the immediately succeeding beds (limestones with dolomi- 

 tized Belleroplion), forms part of the standard limestones. 



Fauna : — 



2. Standard limestones. — Rich, especially in corals and 

 brachiopods ; crinoid-remains ubiquitous. In their fossils the 

 lowest beds differ someAvhat from the rest (pp. 542-43, 546-47). 



1. Modiola phase. — Poor, consisting in most beds merely of 



fish-fragments, abundant ostracods, a Spirorhis-like annelid, 

 or abundant Calcisplicera (!)} The calcareous alga (Girvanella) 

 may be present, poorly preserved, in some coats of the 'piso- 

 liths.' Standard forms — crinoid-ossicles and foraminifera — 

 are known only from rare laminas, in which, however, they 

 are abundant. 



Thickness.— Total, between 200 and 250 feet (Threecliff Bay); 

 350 feet (Longiand Bay). The discrepancy does not appear to 

 be due to faulting. Of the Modiola phase alone, 16 to 20 feet 

 (direct measurement). 



Limits. — The change at the top of the Modiola phase to standard 

 limestones is abrupt, and is accompanied in places by contem- 

 poraneous erosion, which has been sufficient locally, as may be 

 seen in Caswell Bay, to cut out some of the highest beds of 

 the phase. The top of the subzone, that is, C-S, the junction 

 of C, and S l? is not marked by any appreciable lithological 

 change. For this reason, it is frequently useful to 

 group the subzones C 2 and S x as one division, C + S . 



Typical exposures: — 



2. Standard limestones. — Threecliff Bay, east side. Caswell 

 Bay, — several exposures, the southernmost on the east side 

 being the best. Longiand Bay, east side. 



1. Modiola phase. — Threecliff Bay, east side, and Caswell Bay, 

 — several complete exposures at each place, the display in 

 the syncline being particularly good. Note : — The outcrops of 

 the Modiola phase are easily found by reference to the under- 

 lying Oaninia Oolite. 



S = Seminula Zone. 



S., = subzone of Productus ' cora ' D'Orb., mut. S 2 . 

 S x = subzone of Caninia bristolensis Vaughan. 



The subzones were not delimited, nor examined so closely as 

 in the South-Western District ; but the sequence was seen to be 

 much the same as in that district. 



1 The organisms provisionally referred, here and on subsequent pages, to 

 Calcisplicera are isolated spheres of calcite, with an average diameter of 005 

 to 04 mm., the walls of which are thin and have a radial-fibrous structure. 



