330 Reports and Proceedings. 



veiy large proportion of silica, much exceeding that which is ob- 

 tained from rocks of a syenitic nature. These quartziferous rocks 

 form an E.N.E. and W.S.W. course. The arrangement of these rocks, 

 which seem to be quartziferous breccias, is somewhat indistinct. 



In the immediate neighbourhood of St. David's they have asso- 

 ciated with them irregular bands of hard, greenish, ashy -looking 

 shales, much altered in character, but often pi-esenting distinct 

 traces of foliation. In a ridge running from the S.E. of Eamsey 

 Sound in a north-easterly direction the greenish shales are more 

 compact, and resemble earthy greenstones. 



The quartziferous breccias and their associated shales form two 

 anticlinal axes, contiguous to each other, and have on their S.S.E. 

 and N.N.W. sides purple and green rocks. 



The order of the rocks from the quartziferous breccias upwards, 

 when not disturbed by faults, is as follows : — 



Lower Cambrian. 



1. Greenish hornstones on the S.E., and earthy Greenstones on the N.W., forming 



the outermost portions of the so-called Syenitic and Greenstone ridges. 



2. Conglomerates composed chiefly of well-rounded masses of quartz imbedded feet. 



in a purple matrix , 60 



3. Greenish flaggy sandstones 460 



4. Red flaggy or shaly heds, affording the earliest traces of organic remains in 



the St. David's Promontory, namely, Lingulella ferruginea and Leperditia 

 Cmnhrensis 50 



5. Purple (sometimes greenish) sandstones 1000 



6. Yellowish-grey sandstones, shales, and flags, containing the genera P/«<<o««fl!, 



Conocoryphe, Microdiscus, Agnostus, Theca, and Protospongia 150 



7. Grey, purple, and red flaggy sandstones, containing, with some of the above- 



mentioned genera, the genus Paradoxides 1500 



8. Grey flaggy beds 150 



9. The true beds of the " Menevian Group," richly fossiliferous, and the pro- 



bable equivalents of the lowest portions of the primordial zone of M. 

 Barrande 550 



The discovery of a fauna, specially rich in trilobites, among these 

 rocks of the St. David's Promontory, affords very important informa- 

 tion concerning the earlier forms of life of the British Isles. Until 

 the discovery of this fauna, these rocks and their equivalents in 

 North Wales were looked upon as all but barren of fossils. We have 

 now, scattered through about 3000 feet of purple and green strata, 

 a well-marked series of fossils, such as have nowhere else been ob- 

 tained in the British Isles. In the Longmynds of Shropshire the 

 only evidence of the existence of life during the period of their 

 deposition is in the form of worm-burrows, and in the somewhat 

 indistinct impressions, which Mr. Salter regards as trilobitic, and to 

 which he has given the name of PalcBopyge Bamsayi. If we assume 

 the purple and green shales and sandstones, with their associated 

 quartz rocks of Bray Head and the drab shales of Carrick M'Keily, 

 county Wicklow, to represent the old rocks of St. David's, they 

 afford only very meagre evidence of the occurrence of life during the 

 period of their deposition in the form of worm-burrows and tracks, 

 and in the very indeterminate fossils which have been referred to 

 the genus Oldhamia. 



One very prominent feature about the palaeontology of the ancient 



