Vol. 67.] 



SKOMER VOLCANIC SERIES. 



197 



also cut the rocks locally. A little epidote may be present in the 

 centre of some of the decomposed felspar-phenocrysts, and rarely 

 rills vesicles. Apatite is a rare accessory. 



Structurally, the rocks are in no way related to the andesites. 

 With a decrease of ferromagnesian and porphyritic constituents (for 

 instance, E 7046) and the assumption of a good fluidal structure 

 (for instance, E 7112), they pass over in the direction of the 

 mugea rites ; and by the occurrence of large olivines they approxi- 

 mate to the marloesites described below. An intermediate stage 



Fig. 9. 



A=Skomerite, showing subidiomorphic augite and albite-oligoclase felspar- 

 laths ; from the cliffs south of Pigstone Bay (Skomer). Slide E 7090, 

 ordinary light. X 25 diameters. 



B=Mugearite, showing well-defined fluxion-structure, abundant iron-ores, 

 and large apatite close to a small porphyritic augite-crystal ; from 50 yards 

 east of the Limekiln (Skomer). Slide E 7022, ordinary light. X 25 

 diameters. 



may be represented by a flow on the west side of Skomer Island, 

 just above the North Cliff rhyolites (E 7097), which contains more 

 olivine than the typical skomerite, but in smaller crystals than 

 that of the marloesites. 



Chemically, the skomerites would compare very closely with the 

 marloesites (p. 200), from which they differ chiefly in the absence 

 of the glomeroporphyritic groups of albite and olivine. 



